Pwll Mawr Colliery was sunk in circa 1772 by John Smith, on the site of a borehole made by Chauncey Townsend circa 1770. It worked the Great or Six Foot Seam. The shaft was 137 metres deep and was worked until 1828 when a disastrous explosion led to its closure. In 1872 it was aquired by Evan Mathew Richards and re-opened in 1881. The rusticated pump-bob wall remains of the engine-house date from this period. They are located on on the open-ground to the east of the main railway-line leading into Swansea from the north-east. Being the first shaft to reach the Swansea Six Foot Seam in 1770, the present ruin is of considerable historical significance. The mine finally closed circa 1893.

Sources:
A Guide to the Industrial Archaeology of Swansea Region, by Stephen Hughes and Paul Reynolds, AIA, 1989
Site entry by Stephen Hughes for Buildings of Glamorgan, John Newman, 1995

Claire Parry, RCAHMW, 24 August 2011