In 1844 George Insole leased the mineral rights of 375 acres at Cymmer and in 1847 sunk the Cymmer No.1 Colliery and worked the Rhondda No.3 seam. In 1848 36 coking ovens were built on the site.

By 1855 he had sunk the New Cymmer Pit along side the old pit.

On 15th July 1856 a massive explosion at the colliery killed 114 men and boys working underground.

At the coroner's inquest, after hearing the damming evidence given by witnesses to the dangerous state of the mine prior to the explosion, the jury returned a verdict of manslaughter against the manager and four of his officials. However the jury acquitted them at Swansea assizes after guidance for the judge.

The Cymmer new pit shaft was deepened during the 1870's to the Lower five feet seam and the wooden headgear was replaced by one of iron lattice. He also added an upcast shaft, these two shafts being 384 yards and 435 yards respectively.

From the Inspector of Mines list 1896, there were 1,411 men employed at Cymmer New colliery producing Steam coal and 182 at Cymmer Upper producing House and Coking coal.

By 1914 some 2,331 men were employed at Cymmer.

In 1918 there were 780 men working at Cymmer Old pits and 1,553 at the New pit.

The manpower numbered 1,337 in 1938.

This colliery closed in 1940.