The Communist Party USA (CPUSA), officially the Communist Party of the United States of America, is a far-left communist party in the United States. It was established in 1919 in the wake of the Russian Revolution, emerging from the left wing of the Socialist Party of America (SPA). The CPUSA sought to establish socialism in the United States via the principles of Marxism–Leninism, aligning itself with the Communist International (Comintern), which was controlled by the Soviet Union. It was considered to be the most important left-wing organization in the United States through the mid-twentieth century.
The CPUSA's early years were marked by factional struggles and clandestine activities. The U.S.