St Johns Colliery was opened by North's Navigation Collieries Ltd. in 1910 on the site of the recently defunct Cwmdu Colliery (NPRN 86933). In the late 1920s it employed 1,480 workers. The mine is depicted in considerable detail on the 3rd & 4th editions of the Ordnance Survey County series (Glamorgan. XXVI.10 1919, 1937).

This was the last deep mine in the Llynfi Valley, closing in 1985. Remains still visible at the site include large tips.

John Wiles, RCAHMW, 3 January 2008