Butte, Anaconda, and Walkerville supplied much of the copper that helped build the telegraph, telephone, and electrical lines that transformed the United States into a cohesive, industrialized nation. Their industrial landscape, marked by gallows frames and the Anaconda Company smokestack, reflects hazardous mining and smelting work that fostered solidarity among miners and smelterworkers. Butte and Walkerville, known as “The Gibraltar of Unionism,” gave rise to the Western Federation of Miners and the Industrial Workers of the World, whose opposition to “wage slavery” challenged American capitalism. Conflict between labor and capital defined the district, especially after the 1917 Butte Granite Mountain/Speculator Mine fire, the nation’s worst hard-rock mining disaster, which was followed by labor unrest and years of martial law in Butte and by the firing of suspected Socialists and agitators in Anaconda that devastated the unions. During the New Deal, workers in Butte and Anaconda reorganized after the federal government guaranteed the right to unionize, and their four-month industry-wide strike in 1934 helped precipitate the birth of the CIO, which rejuvenated the labor movement nationwide. In 2006, Butte, Anaconda, and Walkerville were recognized as nationally significant for their intertwined mining and labor history; the district covers the years 1876-1934 and spans nearly 10,000 acres with more than 6,000 contributing resources.