Williamstown Welsh: Trewiliam
Williamstown Location within Rhondda Cynon Taf
OS grid reference	ST002907
Principal area	Rhondda Cynon Taf
Preserved county	Mid Glamorgan
Country	Wales
Sovereign state	United Kingdom
Post town	TONYPANDY
Postcode district	CF40
Dialling code	01443
Police	South Wales
Fire	South Wales
Ambulance	Welsh
UK Parliament	Rhondda
Senedd Cymru – Welsh Parliament	Rhondda
List of places UK Wales Rhondda Cynon Taf 51°36′25″N 3°26′31″W / 51.606989°N 3.441819°W / 51.606989; -3.441819

Williamstown (Welsh: Trewiliam) is a village in the Rhondda Valley in the county borough of Rhondda Cynon Taf, within the historic county boundaries of Glamorgan, Wales. Williamstown was founded in the 1870s, is located at the foot of Mynydd Dinas and is a district of neighbouring village Penygraig.

Before the Rhondda was industrialised in the mid to late 19th century, the area where Williamstown now resides, was made up of woodlands occupied by sparsely populated farmlands. Williamstown exhibits very little evidence of early habitation, a few Bronze Age cairns have been discovered on Mynydd Dinas, but most hafodi and farm houses tended to group around the River Rhondda located lower down the valley.

Much of the land in the Rhondda, once controlled by individual farmers, had been bought up by wealthy absentee landlords by the start of the 19th century. The land which would become Williamstown was bought by Walter Coffin, the pioneer of coal mining in the Rhondda, around the 1850s. In 1867 this land was inherited by the Williams family, through their father, a cousin of Coffin. The Williams family gave their name to the town that was built on their land and among the trustees of the family was Caroline Elizabeth Williams, Arthur John Williams and Morgan Bransby Williams.^[1]

• Rhondda Cynon Taf Library Services, Heritage Trail:Penygraig

v t e Rhondda Cynon Taf
Rhondda Cynon Taf County Borough Council
Communities	Aberaman North Aberaman South Abercynon Aberdare East Aberdare West Cwm Clydach Cwmbach Cymmer Ferndale Gilfach Goch Hirwaun Llanharan Llanharry Llantrisant Llantwit Fardre Llwydcoed Llwynypïa Maerdy Mountain Ash East Mountain Ash West Penrhiwceiber Pentre Pen-y-graig Penywaun Pont-y-clun Pontypridd Porth Rhigos Taff's Well Tonypandy Tonyrefail Trealaw Trehafod Treherbert Treorchy Tylorstown Ynyshir Ynysybwl and Coed-y-Cwm Ystrad
Towns and villages	Aberaman Abercwmboi Abercynon Aberdare Abernant Beddau Blaenclydach Blaencwm Blaenllechau Blaenrhondda Britannia Bryncae Bryngolau Brynna Brynsadler Brynteg Buarth-y-Capel Bwllfa Dare Caegarw Carnetown Castell y Mwnws Castellau Cefn Rhigos Cefnpennar Church Village Cilfynydd Clydach Vale Coed-Ely Coedpenmaen Coed-y-Cwm Collena Croesbychan Cross Inn Cwm-Hwnt Cwmaman Cwmbach Cwmdare Cwmparc Cwmpennar Cymmer Dinas Rhondda Dolau Edmondstown Efail Isaf Ferndale Fernhill Foundry Town Gadlys Garden City Gelli Gilfach Goch Glan-y-ffordd Glan-y-llyn Glenboi Glyncoch Glynfach Glynhafod Glyntaff Godreaman Graig Graigwen Groes-faen Hawthorn Hendreforgan Hirwaun Hopkinstown Ilan Llanharan Llanharry Llanilid Llantrisant Llantwit Fardre Llwydcoed Llwyncelyn Llwynypia Maerdy Maesycoed Miskin, Mountain Ash Miskin, Pontyclun Mountain Ash Mwyndy Nantgarw Newtown Pantygraigwen Penderyn Penpisgah Penrhiwceiber Penrhiwfer Penrhys Pentre Pentrebach Pen-y-coedcae Penygraig Penygraigwen Penywaun Perthcelyn Pontcynon Pontsionnorton Pontyclun Pontygwaith Pontypridd Porth Pwllgwaun Rhigos Rhiw Ddar Rhiwsaeson Rhydyfelin Robertstown Roberttown Stanleytown Taff's Well Talbot Green Talygarn Thomastown Ton Pentre Tonteg Tonypandy Tonyrefail Trallwn Trealaw Trebanog Trecynon Treforest Trehafod Treherbert Trenant Treorchy Ty Fry Ty Rhiw Tyla Garw Tylcha Tylorstown Tynewydd Tynybryn Tyn-y-nant Tyntetown Upper Boat Upper Church Village Wattstown Williamstown Ynysangharad Ynysboeth Ynysddu Ynyshir Ynysmaerdy Ynyswen Ynysybwl Ystrad
Education	Aberdare Girls' School Aberdare High School Blaengwawr Comprehensive School Bryn Celynnog Comprehensive School Coleg y Cymoedd Hawthorn High School Mountain Ash Comprehensive School Pontypridd High School Porth Community School St. John the Baptist School Tonyrefail School Treorchy Comprehensive School University of South Wales Y Pant School Ysgol Gyfun Cwm Rhondda Ysgol Garth Olwg Ysgol Llanhari Ysgol Gyfun Rhydywaun
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Topic lists	Parliamentary constituencies Places SSSIs Listed buildings Grade I Grade II* Scheduled Monuments Registered parks and gardens High Sheriffs Lord Lieutenants Museums Public art Schools Place names
Major infrastructure	M4 motorway
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