In the 1920s, after breaking with Garvey, Harrison continued public speaking, writing, and organizing. He lectured on politics history, science, literature, social sciences, international affairs, and the arts for the New York City Board of Education, and was one of the first to use radio to discuss topics in which he had expertise. In early July 1923, he spoke on "The Negro and The Nation" over New York station WEAF. His book and theater reviews and other writings appeared in many of the leading periodicals of the day—including "The New York Times", "New York Tribune", "Pittsburgh Courier", "Chicago Defender", "Amsterdam News", "New York World", "Nation", "New Republic", "Modern Quarterly", "Boston Chronicle", and "" magazine. He openly criticized the Ku Klux Klan and the racist attacks of the "Tulsa Race Riot" of 1921. He worked with various groups, including the Virgin Island Congressional Council, the Democratic Party, the Farmer-Labor Party, the single tax movement inspired by Henry George, the American Friends Service Committee, the Urban League, the American Negro Labor Congress, and the Workers (Communist) Party (the name at that time of the Communist Party USA).