 It also worked with the Durham Miners' Association, Durham Colliery Mechanics' Association and the Durham Cokemen's Association in the Durham County Mining Federation Board.By 1907, membership had reached 2,666.In 1944, when it was known as the Durham County Colliery Enginemen, Boilerminders' and Firemen's Association, it became part of Group No.1 of the National Union of Mineworkers.