Until the middle of the nineteenth century the whole of the Gelligaer urban district consisted of one ecclesiastical parish with St. Catwg's, at Gelligaer Village, as the parish church. There had been no other place of worship available to the scattered parishioners, except the chapel of ease at Brithdir, which was served by a curate until its closure in 1890.
Industrial development in the upper reaches of the Rhymney and Darran Valleys and the subsequent influx and settlement of numerous immigrants, now created a need for spiritual service to people in greater numbers and in places too remotely distant from St. Catwg's which, hitherto, had a flock small in number and sparsely distributed over an area of 16,000 acres.
As a first step in meeting the needs of this quickly increasing population, chapels of ease were built in villages throughout the area. They were served, generally, by resident curates under the direction of the parish priest at Gelligaer, until towards the turn of the century it became necessary to partition the parish into a number of more compact units, and new parishes began to be formed.
A mission church at Pontlottyn was consecrated on the 11th. November, 1863, although a schoolroom had been in use for some time before. The language and character of the church remained Welsh until 1898, when services began to be held in the old schoolroom for English speaking members. The parish of Pontlottyn, covering an extensive area of the northern tip of Gelligaer, was formed on the 4th June, 1870, having St. Tyfaelog's as its parish church, built in the early English style and having an apsidal chancel.
A daughter church, dedicated to St. Teilo, was situated in the village of Troedrhiwfuwch but this was demolished, together with the majority of the hamlet in the 1970’s. This was in use since before 1884. At Tirphil, St. Michael's was opened on the 7th August, 1892, and St. Aidan's, at Newtown, had been served by the clergy of Pontlottyn since 1893.
Fochriw and Deri became a parish in 1923 when it was carved out of the parish of Pontlottyn, St. Mary the Virgin at Fochriw, built in 1907, becoming the parish church.
At the village of Deri stood a mission church which became a Sunday schoolroom when St. Peter's, the present church, was erected. The latter is stone built with a turret containing one bell. An unexpected possession of this modern church is an Elizabethan pewter chalice which was probably brought there from Gelligaer Church when St. Peter's was first being equipped.
St. David's at Pantywaun was built as a mission church in 1869
Places of Worship in Fochriw, Pentwyn, Penybank and Pantywaun
The Anglican churches being St Mary the Virgin in Fochriw, St Andrew’s in Pentwyn Cemetry and St David’s Pantywaun. All were originally Church of England and later the Church in Wales.