Fochriw is a typical south Walian mining village that developed from its rural existence by the need for iron and coal during the 19th century.
It is located on the north-east flank of Mynydd Fochriw at the head of the Bargoed Fach (now called the Darran) valley, approximately 5 miles north of Bargoed and 5 miles south east of Merthyr Tydfil.
The village straddles two ancient hamlets in the parish of Gelligaer these being the Ysgwyddgwyn and Brithdir hamlets, the dividing line being the brook (Bargoed Fach) which flows in the bottom of the valley.
The boundaries of these hamlets were walked by a number of parishioners of the parish on 24th day of May 1750 and a document detailing the boundaries of each hamlet, namely Keven, Hengode, Garthgynyd, Ysgwyddgwyn and Brithdecr (Brithdir) was produced, extracts of same are reproduced below.
It begins where Nant Goch goes to Bargoed by Pont Cradoc then along Nant Goch upwards to the stone standing on the Common opposite Mardy Bach house then from that stone directly westward along the old ditch to the Highway that leadeth from Pen yr Hrwl Ddu to Pen y Bryn Oie then along the way to Trosater Henla then to Three Great Stones standing in the Heath below Twyn y Wayn between Merthyr and Gellygaer then directly eastward to Bargoed River little below the way that leadeth from Keven y Brith
Brithdecr (Brithdir) Hamlet
It begins where Bargoed River goes to Rhymney by Aberbargoed Bridge then along the River Bargoed upwards till it comes very near the way upon the Common that leadeth from Keven y Brith decr to Twyn y Wayn then directly eastwards to the three stones in the Heath below Twyn y Wayn between Merthyr and Gellygaer then directly to the E sid Twyn y Wayn then directly to Fynnon Gwellin then to the old water pond in Pantywayn Coal pits then directly to the spring head of a Brook called Nant y Glynon then to Pwll Elwch Uarc then to Carn y Clyndir or Mark Ycha then to Carn Helig then to Rhyd y Milwr on the River Rhymney then along the River Rhymney to Aberbargoed Bridge aforesaid.
The foregoing boundaries were perambulated the 24th day of May 1750 by George Parry Curate of Gellygaer, William Perrott Churchwarden, Edmond LLewelyn of Garthgynyd, George Williams of Carno, Henry Thomas of Brithdee, Thomas Lewis of Keven Bach, David Evans of Blaen Rhymney, Moses David of Pitwellt, Lewis Edwards of Ysgwyddgwyn and several others of the Parishioners of the said parish