Counter to his mother's wishes for him to become a farmer, Clarke left Georgia in 1933 by freight train and went to Harlem, New York, as part of the Great Migration of rural blacks out of the South to northern cities.
Clarke believed that the credited Greek philosophers gained much of their theories and thoughts from contact with Africans, who influenced the early Western world.
From 1969 to 1986, Clarke was a professor of Black and Puerto Rican Studies at Hunter College of the City University of New York, where he served as founding chairman of the department.
He also was the Carter G. Woodson Distinguished Visiting Professor of African History at Cornell University's Africana Studies and Research Center.
[10] From 1941 to 1945, Clarke served as a non-commissioned officer in the United States Army Air Forces, ultimately attaining the rank of master sergeant.
[11] Traveling in West Africa in 1958–59, he met Kwame Nkrumah, whom he had mentored as a student in the U.S.,[12] and was offered a job working as a journalist for the Ghana Evening News.
[citation needed] On the first anniversary of the Cuban Revolution a group of black civil rights activists, composed of Clarke, Harold Cruse, Amiri Baraka, and Julian Mayfield, travelled to Havana in a trip organised by the Fair Play for Cuba Committee.
Besides teaching at Hunter College and Cornell University, Clarke founded professional associations to support the study of black culture.
He was a founder with Leonard Jeffries and first president of the African Heritage Studies Association, which supported scholars in areas of history, culture, literature, and the arts.