Located within the historic boundaries of Monmouthshire, it is part of the administrative area of the county borough of Blaenau Gwent, Wales.

[2] Located within a narrow valley formed by the River Tyleri, the area now known as Cwmtillery was once wholly a picturesque woodland area based beneath the heights of the local hill 'Gwastad' (551m) to the east and Mynydd James (550m)to the north.

The area was mentioned by English historian William Coxe as "Well peopled, richly wooded and highly cultivated, almost rivalling the fertile counties of England".

[3] During the 1840s, Thomas Brown acquired the rights to sink a mine shaft at the site of a farm known as Tir Nicholas, in the hope of reaching the 'Elled' coal seam.

[5] Cwmtillery was the principal location for the cult experimental feature film The Other Side of the Underneath (1972) written and directed by Jane Arden.