Unions took root in the Wyoming coal fields because of the dangers of underground mining, unfair wages, and the extensive control coal companies exercised over miners' lives. In 1903, the United Mine Workers of America began organizing miners into what became the most powerful union in Wyoming, and by the spring of 1907 it had organized coal miners along the Southern Wyoming Coal Field. Union Pacific Coal Company opposed the UMWA because unionization reduced company control over mining operations, but 1907 brought one of the largest labor strikes in Wyoming history, and pro-union speeches in different languages were enthusiastically received in Sweetwater County. By the end of 1907, Union Pacific Coal Company recognized the UMWA, South Superior had become a union town, and miners gained an eight-hour day instead of ten hours and a wage increase from $3.03 to $3.40 per day. By 1934, miners had achieved a seven-hour day with wages of $5.42 per day. The Union Hall in South Superior was built about 1921 to house union offices and serve as a community center, with a large stage and dance floor on the second floor for plays, concerts, dances, and meetings. Six UMWA locals in South Superior contributed to its construction, and the trapezoid-shaped building is unique in Wyoming.