The Communist Party of the United States of America (CPUSA) is a Marxist-Leninist political party in the United States, established in 1919.
Emerging from the organized Left Wing of the Socialist Party of America, the first American Communists sought to build support among American workers to overthrow capitalism, support the Soviet Union and implement what later was known as Stalinism by establishing a dictatorship of the proletariat in America. Fearful federal authorities reacted with a campaign of suppression, forcing the Communist movement into an underground existence of secret cells, where it was consumed by sectarian political infighting amongst the radicals themselves. At the behest of the Comintern the underground Communist organizations were unified and eased into an above ground existence over the course of the next several years. Bitter factional wrangling continued to grip the party throughout the decade of the 1920s, however, ending in the expulsions of Trotskyist and Lovestoneite factional dissidents.
The coming of the Great Depression and the emergence of fascism in Europe created a great opportunity for the CPUSA to build public support and to expand its role building the US labor movement. The party also was a leading voice in battles on behalf of African Americans, fighting racism in their own ranks and lynchings in the South in seeking social equality of the races. At the same time, the CPUSA aligned itself with the Soviet Union and the ComIntern under the leadership of Joseph Stalin. Elements of the party were systematically employed for espionage on behalf of the Soviet intelligence service.