Oakley Calvin Johnson was an American socialist political activist and writer. A founding member of both the Communist Party of America and the Proletarian Party of America, Johnson is best remembered as a historian of the radical politics of that era.

The Proletarian Party of America (PPA) was a small communist political party in the United States, originating in 1920 and terminated in 1971. Originally an offshoot of the Communist Party of America, the group maintained an independent existence for over five decades. It is best remembered for carrying forward Charles H. Kerr & Co., the oldest publisher of Marxist books in America.