The Western Federation of Miners (WFM) was a labor union that gained a reputation for militancy in the mines of the western United States and British Columbia. Its efforts to organize both hard rock miners and smelter workers brought it into sharp conflicts – and often pitched battles – with both employers and governmental authorities. One of the most dramatic of these struggles occurred in the Cripple Creek district of Colorado in 1903–04; the conflicts were thus dubbed the Colorado Labor Wars. The WFM also played a key role in the founding of the Industrial Workers of the World in 1905, but left that organization several years later.