The Miners' Federation of Great Britain (or MFGB) was established at a conference held in Newport, Wales in November 1889. (A venue chosen for its symbolic significance as it was the fifteeth anniversary of the Chartist Uprising. The MFGB did not begin life as a national union, it had to negotiate with the exisiting regional federations and perusade them to join. South Wales signed up in 1898 but the miners of Northumberland and Durham held out for independence until 1907 and 1908 respectively. By the time of World War I the MFGB was the largest union in Britain with over 600,000 members and remained so until overtaken by the TGWU in the late 1920's.
It was the dispute between the MFGB and the mine owners that lead to the General Strike of 1926 and eventually a humiliating climbown by the miners when even the rest of the trades union movement despaired of their intransigence.
The Miners' Federation of Great Britain became the National Union of Mineworkers in January 1945.