The union was founded by John Kane in 1862 as the Amalgamated Malleable Ironworkers.
He was elected as general secretary, and was able to rapidly increase membership, which reached 14,000 by 1871, and peaked at 35,000 in 1873.
However, after this date, it faced increased competition, particular in Wales, where almost all of its members defected to the rival Independent Association of Tinplate Makers.
[1] In an attempt to recruit more members, the union changed its rules in the 1880s, admitting steelworkers, and paying unemployment benefits, but this had little impact.
Instead, general secretary Edward Trow founded a new union, the Associated Iron and Steel Workers of Great Britain.