James P. Cannon (February 11, 1890 – August 21, 1974) was a leading American Trotskyist. Born on February 11, 1890 in Rosedale, Kansas, he joined the Socialist Party of America in 1908 and the Industrial Workers of the World in 1911. Cannon later joined the Communist Party (CP) and became one of its leading members. The CP expelled him in 1928 for organizing a Trotskyist opposition. Cannon was national secretary of the Communist League of America, and later a leader of the Socialist Workers Party, until his retirement and move to California in 1953.