United Mine Workers of America (UMWA), American labour union, founded in 1890, that engaged in bitter, though often successful, disputes with coal mine operators for safe working conditions, fair pay, and other worker benefits. An industrial union, the UMWA includes miners in bituminous and anthracite coal mines, as well as workers outside the mining industry.
After a successful coal miners’ strike in 1897, John Mitchell became president (1898–1908) and led the union through a period of rapid growth—despite determined opposition by mine operators. Workers staged another successful strike in 1902. By 1920 the UMWA had gained about 500,000 members. Later in the decade the union lost members, strength, and influence because of the emergence of newer, unorganized coalfields in West Virginia and Kentucky (the union was based in the fields of western Pennsylvania and the lower Midwest). The era was also marked by a strong antiunion sentiment.
From 1920 to 1960 the UMWA was led by John L. Lewis, a persuasive labour organizer. In 1933 Lewis capitalized on the pro-labour mentality of the New Deal by organizing the Appalachian coalfields. As a consequence of his success, the UMWA formed the backbone of Franklin D. Roosevelt’s labour support in the 1936 presidential election. Lewis and the union were also a mainstay of the Committee for Industrial Organization (founded in 1935 and renamed the Congress of Industrial Organizations, or CIO, in 1938). In 1942 he withdrew the miners from the CIO, and, except for a brief reaffiliation with the CIO (1946–47), the union remained unaffiliated until 1989, when it joined the American Federation of Labor–Congress of Industrial Organizations. The union earned public criticism for calling a strike in 1943 (during World War II). The action led to the government’s seizure of the mines.
After Lewis retired in 1960, the UMWA experienced unstable and erratic leadership through the early 1980s. One president, W.A. (“Tony”) Boyle (1963–72), was convicted of conspiracy in the 1969 murder of the insurgent union leader Joseph Yablonski and his wife and daughter. Richard Trumka restored a degree of order and democracy to the UMWA upon his election to the presidency in 1982.
The UMWA’s efforts through the first half of the 20th century made American miners among the best-paid and best-insured miners in the world. Its influence has weakened as a result of the combined consequences of automation, the development of alternative sources of fuel, and a general decline in the American labour movement. UMWA membership reached about 500,000 in 1946, but that number dropped below 200,000 in the 1990s. The union had hoped to regain members and influence by calling a lengthy strike in 1993 to protest the opening of nonunion mines, but the unsuccessful strike against the Bituminous Coal Operators Association further weakened the image of the UMWA.