The principal miners' trade union in Britain is the National Union of Mineworkers (NUM), which was established in 1944. It developed from the Mineworkers' (Miners' until 1932) Federation of Great Britain (MFGB), a loose grouping of local associations founded in 1889.
The main archives of the NUM were transferred to the Modern Records Centre between 2022-2024. The documents have gone through a conservation process to help to stabilise them and ensure their long-term preservation, and a project archivist will be working to catalogue the collection between 2023-2026. The NUM archive doesn't include comprehensive national membership records but does contain some area material relating to individual members, particularly for the Yorkshire Miners' Association. We will be making these historic sources available as part of the cataloguing process.
Significant trade union archives relating to the collieries of South Wales are included in the South Wales Coalfield Collection at Swansea University. Other trade union branch and district records can be held by local authority record offices. The National Register of Archives (searchable through the National Archives catalogue) lists some of these.