Green left school and became a coal miner at age 16. He was a subdistrict president of the United Mine Workers of America (UMWA; 1900–06) and national secretary-treasurer (1913–24). Green won appointment to the executive council of the AFL in 1913 and was elected president in 1924. The formation in 1935 of the Committee for Industrial Organization (CIO), headed by John L. Lewis, led to bitter public disputes between the two men, which finally culminated in 1936 in the expulsion of the CIO from the AFL. The two unions were not reunited until 1955, three years after Green's death.