For many years coal mining was the principal industry in the area. Lightmoor coal mine was being deepened in the late 1830s. Trafalgar colliery which was in production in 1860, was the only large mine in the coalfield run by free miners in the later 19th century. Trafalgar closed in 1925. A deep mine, called Northern United, was begun north-west of Cinderford in 1933, but Lightmoor, with a workforce of 600 in 1934, was the main colliery in the Cinderford area until it closed in 1940. There were still many smaller collieries in the Forest of Dean, employing 84.5 per cent of the adult male population in the Cinderford area, until the industry declined in the 1960s.