About the Society
Historical Notes



The oldest secular community in the Cynon Valley is Aberdare (Welsh Aberdâr). It is not known precisely when Aberdare became a settled centre of population but the first known reference to it occurs in a monastic charter of 1203 (see Timeline). The town takes its name from the spot where the afon Dâr flows into the afon Cynon (Welsh aber = confluence). There is no agreement as to the meaning of dâr. It be might be a reference to the profusion of oak trees locally or be descriptive of the tumult of the river [ 1 ].
Historically, the Cynon Valley formed a part of the cwmwd (commote) of Meisgyn (Miskin) and of the cantref of Penychen within the gwlad (kingdom) of Morgannwg/Glamorgan. These were traditional Welsh units of political, social and economic organisation. The name ‘Glamorgan’ is itself an amalgam of Welsh gwlad and Morgan.
The last Welsh ruler of Morgannwg was Iestyn ap Gwrgant who rose to power in 1081. Welsh control of the southern part of Morgannwg ended soon after 1090 when Robert fitz Hamo, a Norman adventurer, and his followers invaded its lowland district (the bro). The Normans displaced the ancient kingdom of Morgannwg and created a marcher (or ‘border’) lordship founded on the continental feudal system of political, economic and administrative management. Meanwhile, subject to an oath of loyalty and service, control of the Glamorgan uplands (the blaenau) was left in Welsh hands until 1246 when local disputes gave Richard de Clare, the then lord of Glamorgan, an excuse to seize the commotes of Meisgyn and Glynrhondda.
Legendary accounts of how political control of Glamorgan was won and lost in the late 11th century are still popularly repeated in this locality as if they were entirely factual. One version, published in the 19th century, went as far as to say “...so the Normans won the lordship of Glamorgan and Aberdare is marked in history by an event which influenced the fate of South Wales” [ 2 ].  The “event” concerned is the mostly imaginary story of how, in 1091, the armies of two Welsh princes (one of whom was allied to the Normans) fought each other near the centre of Aberdare (Maes-y-dre) and on Hirwaun Common, leaving behind them commemorative placenames such as Nant-yr-ochain (Wailing Brook), Bryn-y-beddau (Hill of Graves); Llety Rhys (Rhys’ Lodge); Tudor Terrace and Bron-iestyn.
As the late professor Sir Glanmor Williams has said:

“Many of the picturesque legends surrounding the ‘event’ have had to be exposed by modern scholarship. It is no longer possible to accept the dramatic story of how the Normans were first invited to Morgannwg to assist two Welsh princes, Iestyn ap Gwrgant and Einion ap Collwyn; or how the latter quarrelled and how Einion brought back the Normans to defeat his former ally; or how Fitzhammon immediately parcelled the land of Morgannwg among his twelve knights” [ 3 ].
The marcher lordships of Glamorgan and Gower were joined together by Henry VIII’s Act of Union of 1536 to form the historic county of Glamorgan. This remained in existence until local government re-organisation in 1974.


In 1547 Edward VI made William Herbert, later the earl of Pembroke, lord of Glamorgan. In 1683 the Herbert family’s Glamorgan title and estates passed to Phillip Herbert, seventh earl of Pembroke and subsequently to his great-grand-daughter Lady Charlotte Jane Windsor. In 1766, she married Lord Mount Stuart who later become the first Marquis of Bute.
The 16th century county of Glamorgan continued as a unit of local administration and government from 1536 until 1974 when it was divided into three new counties: those of West, Mid- and South Glamorgan. These counties were abolished in 1996 and were replaced by several smaller, unitary authorities. One of these was the county borough of Rhondda Cynon Tâf of which the Cynon Valley now forms part.
[1] Dr. Brynley F. Roberts ‘Some Aberdare Place-Names’ in Old Aberdare vol. vii, p. 5. (CVHS, 1993)
[2] Bristol Mercury 24 August 1861.
[3] Professor Glanmor Williams, ‘The History & Antiquities of Glamorgan’ in Glamorgan Forests.(HMSO 1961)


The pre-industrial population of the Cynon Valley lived on numerous isolated farms scattered throughout the three historic parishes of Aberdare, Penderyn and Llanwynno (the Mountain Ash district). There was also a small ‘nuclear’ village at Aberdare focused on the late 12th century church of St John the Baptist and comprised of group of humble cottages between the rivers Dare and Cynon.
In an estimate based on the Glamorgan hearth tax assessment of 1670, it is supposed  that about 540 people lived in the parish of Aberdare at that time.
In 1799 a tourist named Robert Clutterbuck wrote that “Aberdare...consisted of near an hundred houses and is remarkable for its neat appearance - not a cot (cottage) but it was as white as milk”. Another visitor, Benjamin Heath Malkin, visiting in 1807 found the village of Aberdare “more populous and better arranged than expected”. Clutterbuck was probably describing only the ‘nuclear’ village of Aberdare since a governmental report of 1831 stated that the number of inhabited houses in the parish as a whole was 218 (1801); 415 (1821) and 809 (1831). [Report of the Parliamentary Boundary Commissioners: part viii; compiled [with a map] by T.F.Ellis and W.Wylde.) In 1828, the parish clerk carried out a census and reported there were 444 houses in the villages of Aberdare, Penywaun, Heol-y-felin, Fforchaman and Llwydcoed.
The first official census in Wales and England was taken in 1801. It recorded only numerical, not personal, information. It showed that the population of the parish of Aberdare that year was only 1,486. The populations of Penderyn and Llanwynno (the correct Welsh spelling) were even lower, being 730 and 426 respectively. Thus, at the dawn of its industrial age, the population of the entire valley numbered only about 2642.


1801 1,486     1891 40,917
1811 2,782   1901 43,265
1821 2,062   1911 50,830
1831 3,961   1921 55,007
1841 6,471   1931 48,746
1851 14,999   1941 43,740
1861 32,299   1951 40,932
1871 37,774   1961 39,155
1881 35,514   1971 37,775

(Figures extracted by D.L.Davies and published in Old Aberdare, vol. ii (1982: p.55) where it is also noted that: (1) no census was conducted in 1941 owing to circumstances of war and that the figure quoted is an estimate made by the Aberdare Urban District Council; and (2) the 1971 census was the last in which the historic parish of Aberdare figured as a distinct unit. In 1974, Aberdare and Mountain Ash were amalgamated to form the Cynon Valley borough authority. It is hoped to add to this section in future (as time allows) extracted figures for the populations of Penderyn and Llanwynno (later the Mountain Ash Urban District) at each of the decennial census between 1801 and 1970.


In 1536, Henry VIII’s Act of Union provided that “Glamorgan...be represented in the House of Commons by a Knight of the Shire…”. In effect, this meant that the wealthiest landowning interest, rather than the people as a whole, was represented in parliament. The first M.P. for the county of Glamorgan was George Herbert of Swansea (elected 1542); the last, before changes brought about by the Reform Act, was Lord Patrick J. H. Crichton-Stuart (returned 1831).
The Reform Act of 1832 granted a parliamentary seat to a new industrial district centred upon Merthyr Tydfil. This became a ‘parliamentary borough’ which included the historic parishes of Aberdare and Llanwynno, though not Penderyn (which remained within the county of Breconshire until 1974). The first borough members were: Sir Josiah John Guest (1832–52) and Henry Austin Bruce, later the first Lord Aberdare (1852–68).
The Reform Act of 1868 awarded a second seat to the parliamentary borough on account if its considerable growth in population. The ‘dual membership’ was as follows (with the ‘senior member’ noted first):

Richard Fothergill & Henry Richard:    1868–1874
Henry Richard & Charles Herbert James: 1874–1888
David Alfred Thomas & William Pritchard Morgan: 1888–1900
David Alfred Thomas & James Keir Hardie: 1900–1910
James Keir Hardie & Edgar Rees Jones: 1910–1915
Edgar Rees Jones & Charles Butt Stanton: 1915–1918

In 1918, the separate parliamentary constituency of ‘Aberdare’ was created. It consisted of the two urban district authorities of Aberdare and Mountain  Ash. In 1974, the name of the seat was changed to ‘Cynon Valley’ in order to reflect major local government re-organisation. Those returned as members of parliament were:
Charles Butt Stanton:    1918–1922
George Henry Hall:    1922–1946
David Emlyn Thomas:    1946–1954
Arthur Reginald Probert:    1954–1974
Ioan Lyonel Evans:    1974–1984
Ann Clwyd    1984–2019
Beth Winter    2019 to date



The main economic activity of the area during the pre-industrial era was, of course, farming and a small agricultural sector remains active - especially towards the north of the district (in the Penderyn district). The major industries of the locality since the dawn of the 19th century have been firstly iron and subsequently coal.
There have been other industries of note that have flourished at various times during the past two centuries. These have included: the Gadlys Tinplate Works; the Cambrian Lampworks (manufacturers of the internationally-employed ‘Thomas & Williams Safety Lamp’); brewing; brick-manufacturing; iron-founding; printing; boot- and shoemaking; tanning; quarrying and light engineering.


c.750–600 B.C.   A hoard of Bronze and Iron Age weapons, tools and utensils of this period were discovered in Llyn Fawr above Rhigos between 1911–13. They are thought to have been offerings to the gods of the time.
c.75 BC.   Roman soldiers construct and maintain a marching camp at Twyn-y-Briddallt above Cwmaman.
c.AD600   Gwynno, a lesser saint of the Celtic Church, establishes a small cell and community at Llanwonno.
c.600–1100   During the early medieval period, the inhabitants of the area sustained a traditional pastoral way of life with social, economic and personal relationships based on the indigenous Welsh lawcode of Hywel Dda (‘Cyfraith Hywel’).
c.1090   Norman incursions into Glamorgan lead to the loss of native Welsh lordship in its southern parts and the creation of the feudal lordship along continental lines.
c.1190   Approximate date of the foundation of St. John Baptist church, Aberdare: firstly as an outlying ‘chapel-of-ease’ to the parish church of Llantrisant. Only much later (in the mid-19th century) did it acquire the status of a parish church. Evidence for its late-12th century foundation is based on an assessment of its architectural character.
1203   An agreement between Margam and Llantarnam abbeys concerning their respective grazing rights over Hirwaun Common (‘Hirwaun Wrgant’ by its full, historic name) makes specific mention of Aberdare for the first time.
1229   Hywel ap Maredudd unites the commotes of Miskin and Glynrhondda.
1246   The last Welsh ruler of Miskin, Hywel ap Maredudd, was displaced by Richard de Clare, Norman lord of Glamorgan.
c.1290   Grant of three farms - Hendre Beili and Tir yr Ergyd (Llwydcoed) and Ffaldau (Fforchaman) - to the monastic manor of Penrhys in the Rhondda, an outlying interest of Llantarnam Abbey.
1349   All ecclesiastical taxes (tithes) payable annually to the church in Aberdare awarded henceforth by Hugh le Despencer, lord of Glamorgan, to Tewkesbury Abbey in Gloucestershire.
1520–1663   A time which saw the emergence of early, but small-scale, iron working in the Cynon Valley with blast furnaces at Dyffryn, Mountain Ash (1586); Cwmaman (c.1600) and Llwydcoed (1663). There is also a claim that a similar furnace operated near Hirwaun, in the parish of Penderyn, circa 1660 though the evidence for it is (as yet) uncertain.
1541   The payment of tithes from Aberdare is transferred from Tewkesbury Abbey to Gloucester cathedral as an aspect of the Dissolution of the Monasteries.
1601   Likely division of the parish of Aberdare into its four pre-industrial ‘hamlets’ in order to apply Elizabeth I’s Poor Law Act of that year. The hamlets were: Cwmdare (including Aberdare); Llwydcoed (inc. Hirwaun), Cefn Pennar (inc. Cwmbach) and Fforchaman (the entire Aman Valley as far as the Rhondda Fach). This division may have originated earlier as a consequence of the Highways Act of 1555 which placed responsibility for repairing the few local roads on the parish and created the office of Surveyors of Highways for that purpose.
1637   Aberdare’s principal landowner of the day, William Mathew of Aberaman, presents a dated bell to St. John Baptist church.
c.1724   Eleanor Mathew of Aberaman endows almshouses in the village of Aberdare, near the site of the present library, to accommodate four poor persons.
1751   Founding of the first nonconformist chapel in the Cynon Valley at Hen Dŷ Cwrdd (‘The Old Meeting House’), Trecynon. Its origins go back to an earlier cause at Cwm-y-glo (1689), Heolgerrig. This served those in the Aberdare, Merthyr and neighbouring  districts who risked dissent from the established Anglican Church. The origins of Cwm-y-glo, in turn, extended back to c.1650 and the time of the Puritan Commonwealth.
1757   The opening of an ironworks at Hirwaun by John Mayberry of Brecon brings larger-scale industry to the Cynon Valley for the first time.
1772   Aberdare and Llanwynno become perpetual curacies. (i.e. formally separated from the parish of Llantrisant for the first time).
1790   Establishment of the Aberdare Canal Company by act of parliament.
1793   The Aberdare Turnpike Act was passed authorising a road through the valley northward from Navigation (Abercynon). Work commenced 1803, and was completed soon after 1810.
1795   Vestry annex added to the parish church.
1801   The Scale family from Handsworth, Staffordshire, began their Llwydcoed ironworks.
1807   “Exquisitely beautiful and verdant”  (the description of the Cynon Valley by Benjamin Heath Malkin).
1812   The Aberdare Canal opened for traffic and joined the Glamorganshire Canal (between Merthyr Tydfil and Cardiff) at ‘Navigation’ (Abercynon).
1824   Opening of National (Anglican) School at Aberdare.
1827   Opening of the Gadlys Ironworks by father and son Mathew and Thomas Wayne on part of the Gadlys Isaf estate of Edward Morgan Williams and George Rowland Morgan, landowners.
1827–28   The rural setting of the village of Aberdare and of the Cynon Valley as a whole recorded in pencil sketches by sisters Emma and Lucy Bacon of Aberaman House.
1832   The Parliamentary Reform Act passed creating the new constituency of ‘Merthyr Boroughs’: i.e. Merthyr Tydfil and Aberdare together (see Introduction).
1837   The sinking at Abernant-y-groes, Cwmbach, of the valley’s first deep coalmine by Thomas Wayne in association with the David family, landowners.
1838   It was reported that 60,898 tons of iron were sent down the Aberdare Canal to Cardiff.
1844   Detailed survey of land in the parish of Aberdare undertaken as a result of the Tithe Commutation Act, 1836. A Schedule  with land valuations was produced in 1844 and a Map in 1847. Similar tithe records were compiled for the parishes of Penderyn (Schedule, 1839; Map, 1841) and Llanwynno (Schedule, 1841; Map, 1842).
1845   Opening of the Aberaman Ironworks by Crawshay Bailey.
1846   Opening of the Aberdare Railway which ran from Abercynon to Mill Street (Heol-y-felin/Trecynon). The Aberdare line was leased that same year to the Taff Vale Railway Company.
1846   The Marquis of Bute, as lord of the manor (or ‘lay proprietor’) endows the appointment of the Rev. John Griffith as vicar of Aberdare which becomes thereby an ecclesiastical parish in its own right for the first time.
1847   Publication of the Report of the Commission on Education in Wales (widely termed ‘Brad y Llyfrau Gleision’/‘The Treachery of the Blue Books’.)
1848   Establishment of a British (i.e. non-denominational) School at Ysgol y Comin (Park School), Trecynon.
1848   Establishment of the Aberdare Gas Company at Abergwawr, Aberaman, marks the beginning of street-lighting and the provision of gas as a public utility.
1849   Outbreak of cholera at Aberdare results in 104 deaths.
1849   County Highways Board set up to maintain county roads in the district; and a surveyor appointed to maintain a system of some 35 miles.
1849   Explosion at Llety Shenkin colliery, Cwmbach with the loss of 53 lives. Among those killed were twelve boys: one aged 8; one aged 10; two aged 11; two aged 12; three aged 13; one aged 14 and two aged 15.
1850–60   Decade of intense building development in Aberdare town-centre and outlying districts.
1851   The Vale of Neath Railway (the ‘High Level Line’) reached Aberdare. The main route ran from Neath to Merthyr with a branch to Aberdare at Gelli Tarw (Llwydcoed).  The Dare-Aman Branch between Cwmdare and Cwmaman, with its junction at The Cwm, Gadlys, was added in 1853.
1852   An explosion at Middle Dyffryn colliery, Cwmbach, killed 65 colliers.
1852   St Elvan’s Church opened in October this year.
1852   Henry Austin Bruce, later Home Secretary under Gladstone and then first Lord Aberdare, elected M.P. for Merthyr Tydfil and Aberdare.
1853   Report of T.W Rammell to the General Board of Health in London on the “Sewerage, Drainage and Supply of Water, and the Sanitary Condition of the Inhabitants of the Parish of Aberdare”… (the ‘Rammell Report’).
1853   Aberdare’s new Market Hall and slaughterhouses opened. Thomas Dafydd Llewelyn and Thomas John Jones submit essays on the history of the district to Eisteddfod Y Carw Coch held at the Hall that year. These are published in the volume Gardd Aberdâr the following year.
1853    The Vale of Neath railway company extended its line from Gelli Tarw to Merthyr Tydfil; it also opened its Dare Valley branch, reaching the pits of Cwmdare; by 1856 the branch was extended to the pits of Cwmaman. The Dare Valley branch required the building of two wooden viaducts: the Gamlyn traversing the River Cynon and The Cwm viaduct crossing the River Dare.
1854   Creation of a Local Board of Health under the Public Health Act of 1848 as a result of T.W. Rammell’s Report. Its aim was the improvement of public health in the wider district.
1857   The Vale of Neath Railway was extended from Aberdare to Quaker’s Yard enabling through trains to run from Neath to Pontypool.
1858   Formation of Aberdare Water Works Company to provide a public supply of clean water. The Temperance Hall (Palladium) in Canon Street was opened as Aberdare’s first public meeting hall and theatre.
1858–90   The ‘golden era’ of Aberdare as a centre of printing and publishing in Wales. The industry retains a presence in the locality until the 1960s.
1859   A religious revival occurred locally and in much of Wales. The cymanfa ganu as a continuous Welsh religious and cultural phenomenon began at Aberdare with singing festivals at Bethania chapel and the Temperance Hall.
1860   The first Co-operative society and shop in Wales opens at Cwmbach on 8 March.
1860   E. Thomas Cambrian Lampworks begins trading, initially at Evan Thomas’s ironmongery shop at 7 Cardiff Street, (and from 1877 at Graig Street). Lewis Noah Williams joins Thomas some years later. Williams’ first appears in the company name in December 1887, nine months after the death of Evan Thomas.
1860   The early 1860s sees the opening of Aberdare Cemetery on Hirwaun Common.
1861   Publication of the Aberdare Times (which continues until 1902).
1861   The first National Eisteddfod of the modern era held at Aberdare Market Hall.
1864   St Mair’s Church opens and is consecrated. A church built for the Welsh speaking Anglican congregation of the Aberdare Parish.
1865   The Mimosa sailed from Liverpool to Patagonia in an attempt to establish an independent Welsh colony in the southern hemisphere with almost 40% of the contingent hailing from the Cynon Valley and Merthyr Tydfil.
1867   A Local Board of Health established specifically for Mountain Ash.
1868   A further Parliamentary Reform Act awarded the Merthyr Boroughs constituency (of which Aberdare formed part) a second M.P. Richard Fothergill of Abernant, a local ironmaster, and Henry Richard, an avowed nonconformist and peace-campaigner are returned. Henry Austin Bruce lost his seat (but is found another, in Scotland, by Gladstone).
1869   Aberdare Public Park opened over approximately 50 acres of what had been a part of Hirwaun common; and a new Aberdare and Aberaman Gas Company was formed.
1872–3   Victories of the celebrated South Wales Choral Union (‘Y Côr Mawr’) led by Griffith Rhys Jones (Caradog), at the Crystal Palace, London.
1881   A cottage hospital endowed and opened at ‘The Trap’, Abernant Rd., by the third Marquis of Bute, a Catholic convert, and staffed by nuns.
1885   The National Eisteddfod returned to Aberdare. The Maes was in Plasdraw, at a location that is later to be occupied by the Girls’ County School.
1892   St Michael’s Theological College opens in March. It occupies Abernant House. However, in 1907 the college relocates to Cardiff.
1894   Formation of the Aberdare Urban District Council and Mountain Ash U.D.C.
1895   The Richard Bowen Jenkins Memorial Hall is erected in Seymour Street, Aberdare. (It is demolished in 1989).
1896   The Aberdare Intermediate School, the town’s first secondary school, opens in Trecynon. Headmaster: W. Jenkyn Thomas, M.A.
1897   In June, Queen Victoria’s Jubilee is celebrated. The ceremony to unveil an ornamental drinking fountain in Commercial Place is not cancelled even though the fountain had not been delivered to the town.
1900   Electricity introduced in the Aberdare area and formal closure of the now redundant Aberdare Canal.
1900   Election of James Keir Hardie as the first Independent Labour M.P. in Wales, being without formal association with the Liberal Party.
1902   First appearance of the Aberdare Leader (which continues to date, in different circumstances, as the Cynon Valley Leader).
1904–5   The ‘Religious Revival of Evan Roberts’ began to assume a Wales-wide momentum following Roberts’ visit to preach at Bryn Seion Methodist chapel, Trecynon in 1904.
1905   The National Eisteddfod held at Mountain Ash.
1905   Dr Teddy Morgan, brought up in Agents Row, Abernant, scores the winning try whilst playing as a member of the Wales XV who beat the 1905 New Zealand touring All Blacks rugby football team.
1907   Mountain Ash County School opens at Gwernifor, Miskin. First headmaster: Watkin Uthur Williams, M.A.
1910   The 1910 “Block Strike” begins in October and lasts 10 weeks but with lasting effects well into 1911. Serious civil unrest, particularly in Aberaman. Dispute was between the Powell Duffryn Steam Coal Company and its employees. There were many grievances, but the strike took its name from the management decision at Lower Duffryn Colliery to withdraw the established custom whereby miners were allowed to take home scrap wood for firewood.
1910   William Haggar, pioneer of the cinema in Wales, opens his ‘Coliseum Bioscope Theatre’ on Aberdare Market yard.
1912   The area’s first purpose-built, permanent ‘picture palace’, the ‘Aberdare Electric Cinema’ opened at Cardiff Street in the town-centre.
1912   George V and Queen Mary visit the town in June of this year.
1912   William Haggar, pioneer of the cinema, builds the Kosy Cinema in Market Street, Aberdare, on the site of the old Drill Hall opposite the Market Yard.
1913   Electric tram cars introduced by the local authority on designated routes. Trackless electric vehicles, (trolleybuses), were introduced soon afterwards to serve Cwmdare from the Trecynon Cemetery tram terminus, Capcoch from the Aberaman terminus, Cwmaman from the Aberaman terminus and Abernant from Aberdare.
1913   The Intermediate School for Girls opens in Plasdraw. First headmistress: Miss Margaret S. Cook, M.A.
1914  The bridge connecting Robertstown, also known as Tresalem, to the bottom of Tudor Terrace is formally opened in December. The contract price was £2,500 and the builder was Mr D. Tyssul Davies of Trecynon. Prior to its opening, access into and out of Robertstown was by the footbridge across the Cynon onto the tramway. Initially for pedestrians and light vehicular traffic, its opening followed a great deal of petitioning by the inhabitants. The Aberdare Leader reported the opening ceremony using Pont Salem for the name of the bridge.
1914–18   The First World War greatly affected this and every other district. By November 1918 there had been 700 fatalities from the Aberdare urban district.
1917   The Aberdare & District General Hospital opened at Abernant House (previously the home of the Fothergill ironmaster and later of St. Michael’s Theological College).
1918   The Cynon Valley (as ‘Aberdare’) became a parliamentary constituency in its own right. Its first M.P. was the maverick character Charles Butt Stanton: previously a Labour activist but elected in 1918 for the short-lived National Democratic Party which he helped found.
1920   In July the statue to commemorate Caradog, Griffith Rees Jones, and his victories as conductor of the Côr Mawr at the Crystal Palace in 1872 and 1873, is unveiled by Lord Aberdare.
1921   Aberdare Athletic Football Club became members of the Football League (Division Three South). They played teams such as QPR, Norwich City, Southampton and Swansea Town. Their matches were played at the Aberdare Athletic Ground at The Ynys. The team was relegated in 1927.
1921   Formation of  Aberdare Golf Club.
1921   Formation of  Cwmbach Male Voice Choir.
1922   The tramway system is extended to Cwmaman and Abercwmboi replacing the ‘rail-less bus system’ (trolleybuses) to these destinations. Trolleybuses are also withdrawn on the Cwmdare route.
1923   The Cenotaph in Aberdare is unveiled in March by Sir D.R. Llewellyn.
1925   The ‘rail-less bus system’ (trolleybuses) to Abernant is withdrawn.
1926   Mountain Ash County School moves to Dyffryn House, former home of Lord Aberdare.
1926   A major dispute across the south Wales coalfield as elsewhere in Britain led to a prolonged miners’ strike, lock-out and much hardship between 1st May and 2nd December. A British-wide General Strike in support of the miners lasted barely a week before collapsing. The outcome of the bitter confrontation was the widespread blacklisting of strikers; a 20% reduction in wages and the imposition of an eight hour day on those workers who were able to return to work.
1928  Plaid Cymru’s first branch outside Caernarfonshire is established in the vestry of Bethesda chapel, Abercwmboi.
1929   Fire destroys the main building, previously Abernant House, of Aberdare Hospital in September of this year. Lieutenant William George Pink & Fireman Reginald Jenkins of the Aberdare Brigade are killed & Fireman Grinter seriously injured whilst tackling the blaze. 80 patients are successfully evacuated.
1930   March 1st, thousands gather in Aberdare for the funeral of Welsh Salvationist Mother Shepherd, [Pamela Shepherd]. The service takes place at Trinity chapel and more than a thousand attend at the graveside in Aberdare Cemetery. She died at her home, 7 East Avenue, Aberdare, on 24 February 1930. Mother Shepherd was born in 1836 at Talywain, Monmouthshire. After many years in London, she was sent to Aberdare in 1878, as a native speaker of Welsh, to begin her mission. After several other postings throughout Britain she returned to Aberdare in her retirement, and Pamela Shepherd became the first Probation Officer in Trecynon in 1907.
1930   The Mardy House Central Schools opens in the grounds of Mardy House. The house at an earlier time belonged to Lord Merthyr, (Sir W.T. Lewis). This central, or senior, school draws its pupils mainly from the three National elementary schools: Aberdare, Cwmbach and St Fagan’s, Trecynon. It is the first Church Secondary School in Wales.
1930s   A prolonged economic depression ensued and blighted the lives of a generation across  the south Wales coalfield, linked as it was to a contraction of the coal industry and the crisis in international finance following the ‘Wall St. Crash’ of 1929. The decade was a time of mass unemployment and of continuous and heavy migration from the Cynon Valley and similar mining communities.
1931   On land and in an old locomotive shed donated by the Llewellyn family of Bwllfa, The Little Theatre opens in the Gadlys.
1933   Re-opening of Aberdare General Hospital by HRH the Duchess of York, 25 April. The Rev. R. Ivor Parry commences his pastorate at Siloa Welsh Congregational Chapel, Aberdare. His predecessor, Rev. D. Silyn Evans, occupied the post for 50 years, 1880–1930.
1934   Rt. Hon. Lloyd George visits Aberdare Hospital in May.
1935   The last tram runs, from Aberaman to the depot in the Gadlys.
1936   The Aberdare Valley Educational Settlement (Coleg Gwerin Cynon, Aberdâr) opens in Fairfield House. The house is donated by Captain & Mrs M.H. Llewellyn to the King George VI Jubilee Trust, who in turn transfers it to the Welsh Branch of the National Council of Social Service for use as an adult educational settlement. An Aberdarian, Mr. J. Victor Evans, is appointed as its first Warden.
The son of H.H. Evans, General Manager Cambrian Collieries, Mid-Rhondda, John Victor Evans lived at Park Isaf, Cwmdare. After school, (one year at Aberdare County School, then Christ’s College, Brecon for the remainder of his secondary education), he joined the army; went up to St John’s College, Oxford where he took a degree in History, and was President of the Union, 1922. After Oxford he became a barrister and then a lecturer at UCW, Aberystwyth, before returning to Aberdare.
1936–1939   The Spanish Civil War. Ten volunteers from the Cynon Valley joined the International Brigade to fight against fascism in Spain.
1937   Visit of George VI and Queen Elizabeth to Aberdare, 16 July.
1937   The manufacturing firm ‘Aberdare Cables’ arrives in Aberdare.
1938   Production commences at the Aberdare Cables factory in Trecynon - beginning of diversification of employment in the area away from the coal industry.
1938   The Coliseum opens in September, at this time called The New Welfare Hall.
1939   The 1250-seat cinema The Rex opens. (It closes in 1983, and is demolished in 1990). Before closing it plays a starring role in the film Coming Up Roses, and the Welsh version Rhosyn a Rhith (1986). The film was screened at the 1986 Cannes Film Festival.
1939–45   Second World War.
1941   A German aircraft flying (it’s believed) to and from Swansea on a bombing mission discarded bombs over Cwmbach on 30th May, killing four people and badly damaging Bethania Welsh Baptist chapel. Collateral damage was suffered in Abernant and Cwmdare.
1941   The Royal Ordnance Factory built near Hirwaun to produce munitions for the war effort, making extensive use of female labour.
1944   Alun Lewis, the Cwmaman-born poet and short-story writer dies in Burma, aged 28.
1946   The Wales & Monmouthshire Estate Company takes over the former Royal Ordnance Factory at Hirwaun as part of a post-war economic recovery programme in distressed mining areas. It becomes the focus of a ‘trading estate’ which, by 1961, housed 23 firms employing 6,000 workers, mostly in light engineering and the manufacture of electrical goods.
1946   The National Eisteddfod held at Mountain Ash, where Princess Elizabeth (later Queen Elizabeth II) was admitted to the Gorsedd of Bards.
1947   Nationalisation of the coal industry and the acceleration of its long decline until 1995 when only one deep mine remained in Wales - Tower, Hirwaun.
1948   Chief Inspector Fabian of Scotland Yard arrives in Aberdare to investigate the murder of Jerzy Strzadala in Aberdare Park. The case has not been solved.
1949   The establishment of the Aberdare Welsh Primary School in Aberdare: one of three such schools that were established this year, following the first which opened in Llanelli in 1947.
1950   Whilst at Aberdare Rev. Gwilym Tilsley wrote Awdl Foliant i’r Glöwr, (Ode in Praise of the Miner), one of the most famous and popular in the twentieth century.
1950   In July a Dr Barnardo’s Home opens in Glandare House. The first Superintendent is Henry Gratwick.
1953   Great excitement in Aberdare and Hirwaun in July as the newly crowned Queen, and Duke of Edinburgh, travel through the town to Hirwaun station where they board the Royal Train to Swansea. A welcome arch is constructed near the top of Monk Street, and the route through the town to Hirwaun is heavily populated with well-wishers and bunting.
1956   The National Eisteddfod returned to Aberdare for the third time, being held at Aberdare Park.
1957   The Aberdare Leader’s talking newspaper for the blind commences.
1957   The Glamorgan County Council Planning Department produces a radical plan for the redevelopment of Aberdare. 3000 houses and some public buildings would need to be demolished. Opposition to the plan leads to the formation of the Protectionist Association who take a third of the seats from the Labour Party at the following local elections. A protracted Public Inquiry follows, where counsel for the main body of objectors were Roderick Bowen, Q.C., M.P. and Tasker Watkins, Q.C., V.C.
1958   A deputation protesting against The Aberdare Town Plan travels to the Welsh Office, Cardiff, in October.
1958   One of the most prominent women in the Labour Party in Wales in the first part of the twentieth century, Alderman Florence Rose Davies, CBE, JP, dies. Amongst her many achievements was that she became the first woman to lead the Glamorgan County Council, 1949–50. She was born in 1882 in Cardiff Street, Aberdare, the granddaughter of the Victorian photographer J. Lendon Berry.
1958   The Nos Galan road race is held for the first time in the Llanwynno and Mountain Ash district. There were no races in the years 1974 to 1983 inclusive, but they were reinstated in 1984 and now continue to draw large crowds to the area on New Year’s Eve.
1961   The Urdd National Eisteddfod takes place in Aberdare.
1963   The new Aberdare Central Library is formally opened in September by Councillor S. Wilcox, Chairman of the Council. A commemorative plaque is unveiled by The Rt. Hon. Sir Keith Joseph, Bt., M.P., Minister of Housing and Local Government, & Minister for Welsh Affairs.
1964   Closure of railway passenger services on both the High Level (ex-GWR and Vale of Neath) and the Low Level (ex-TVR and GWR) - victims of The Beeching Axe.
1965   Fforchaman Colliery was closed. This was the last deep mine worked from within the old parish of Aberdare.
1966   Selective secondary education ceases in the Mountain Ash and Penrhiwceiber areas with the conversion of Mountain Ash Grammar School to Mountain Ash Comprehensive School, and similar changes at Abertâf and Bryngolwg Schools.
1967   William Watkin Price, doyen local historian, dies at the age of 94.
1969   In July, The Prince of Wales visits Aberdare Library as part of his tour of Wales.
1970   The Dr Barnardo’s Home at Glandare House closes in December. The House is demolished in May 1971.
1970   The Gas Council published plans for LNG (Liquefied Natural Gas) storage tanks near Hirwaun. A bitter and long running dispute against the development led by residents of Hirwaun ensued. After several years, they won their battle and eventually building work commenced in the spring of 1978 at an alternative site, Dynevor Arms, on the Merthyr Mountain. The LNG facility closed 31 years later in 2009.
1971   Formation of the Cynon Valley History Society. Dr Alistair Wilson, Mr Ken Rees and Mr J.F. Mear are elected chairman, vice-chairman and secretary respectively.
1973   The Dare Valley Country Park opens. The visitor centre and camping ground are constructed on the site of Bwllfa No.3 Colliery, (Powell’s Pit). Over the previous two years, an enormous effort has been made to clear the tips and buildings associated with Bwllfa No. 1 and Nantmelyn Collieries. The River Dare has been re-routed and two lakes created.
1974   The Cynon Valley Borough Council is established, replacing the Aberdare and the Mountain Ash Urban District Councils.
1974   The 1974 Miners’ Strike began in February and ended the following month following a 35% pay offer from the new Labour government.
1975   In January, Mardy House Secondary School transfers to new buildings at Glandare. At a later date, Aberdare Town (Church in Wales) Primary School transfers to the old Mardy House site, vacating its Cardiff Street buildings which it had occupied since 1829. The Cardiff Street school, known as “The National,” was opened by the National Society for Promoting Religious Education. These schools provided elementary education, in accordance with the teaching, at that time, of the Church of England.
1976   On March 4th, Mardy House School is re-opened, dedicated and named St John Baptist Church in Wales (Voluntary Aided) Secondary School.
1978   Selective secondary education ceases in the upper Cynon Valley. In Aberdare, two single-sex comprehensive schools are created in existing buildings constructed at the turn of the century, whilst a mixed comprehensive school opens in newer buildings, (1974), previously occupied by a secondary school at Blaengwawr. St John Baptist Church in Wales (VA) Secondary School, Glandare is the fourth school in the scheme.
1979 Exceptionally heavy rain on Boxing Day brings serious flooding throughout the valley.  
1983/84   Major works started in order to build the Aberdare bypass. It utilises ex-TVR railway land which stretches from Aberaman to Robertstown. Several landmark buildings are demolished in the area of ‘Smith’s Corner’.
1984–85   The last major strike of miners, locally and throughout Britain, indicating that an important period of industrial history in this area and nationally was coming to an end.
1988   Abercynon Colliery closes; the last deep mine working in the old parish of Llanwynno.
1988   In July, The Prince of Wales opens a new Pirelli General factory at Trecynon.
1988   Railway passenger services restart in Aberdare using a modified High Level station, and then on a route from Cwmbach to Abercynon on ex-Low Level track via a new River Cynon crossing.
1989   The Cynon Valley Borough Council purchases The Coliseum.
1991   The Phurnacite Plant in Abercwmboi closes. It produced smokeless fuel in the form of briquettes for 50 years. At its peak over one million briquettes were produced each year. The plant was the source of much atmospheric pollution in the Cynon Valley and of subsequent health problems for its employees.
1993   Mardy House is demolished. Its last use was as a tax office on the ground floor, and accommodation for church curates on the upper floors. At a later date, The Beeches Care Home is built on the site of the old house.
1995   The opening of the area’s first Welsh-medium secondary school at Rhydywaun, serving both the Cynon and Tâf valleys.
1995   Major extensions to The Coliseum are completed.
1996   The Cynon Valley Borough Council is abolished and a new unitary authority created, Rhondda Cynon Tâf. This was the first time in over a century that the Cynon Valley was not a centre of local government.
2001   The Cynon Valley Museum & Gallery opens, situated on the site of the 19th century Gadlys Ironworks.
2008   Closure of Tower Colliery, Hirwaun; the last deep mine in the Cynon Valley and the whole of Wales.
2012   The £70m Ysbyty Cwm Cynon opens replacing Mountain Ash and Aberdare hospitals.
2013   The headteacher of Aberdare’s new school is appointed in February. A start is made on the construction of the school to be built at The Ynys. The new school will replace Aberdare High School, Cwmdare Road; Aberdare Girls’ School at The Gadlys and Plasdraw; and Blaengwawr Comprehensive School. The schools to be closed have origins going back to 1896, 1913 and 1974 respectively. Blaengwawr has an earlier antecedent at Aman Secondary School, Godreaman, which opened in the early years of the twentieth century.
2013   The 2013 Review of Parliamentary Constituencies in Wales whereby the Cynon Valley Parliamentary Constituency would have been dismantled is cancelled.
2013   Aberdare Hospital in Abernant is demolished.
2017   Friday, 24th February marked the last day of coal-train workings from the old tower washery site to Aberthaw Power Station. Probably the last coal train to leave the Cynon Valley since the Aberdare Railway opened in 1846.
2017   In October a new Further Education College at Aberdare was officially opened by First Minister Carwyn Jones and Dr Lyn Evans of CERN. The new building is located near Aberdare railway station. It replaces the old college on Cwmdare Road which was opened in September 1954.
2018   In October, Cwmaman-born Olympic sprinter Ron Jones, 84, opened a new £3m athletics stadium at the Ynys. Ron Jones first ran for Wales at the Cardiff Empire Games in 1958.
2019   Aberdare Park 150th anniversary celebrations took place on July 11th. The day-long programme included choral singing events and a re-enactment of the opening ceremony of the Park.
2019   At the general election on December 12th, Beth Winter, Labour, was elected as MP for the Cynon Valley. She replaced Ann Clwyd who held the seat 1984–2019.