Marcus Garvey founded UNIA in Kingston, Jamaica (1914). Immigrating to Harlem in 1916, he rebuilt it amid the Great Migration and World War I. UNIA preached black pride, self-help, Back-to-Africa, and African independence.

Its message attracted the African American masses, notably poor migrants from the rural South. Chapters formed across the country, in Central and South America, the West Indies, West Africa, England, and Canada. UNIA enlisted more than a million members by 1920. It sponsored uniformed corps, including the Black Cross nurses and Legions; it had parades and rallies to honor Africa and the race. The Negro Factories Corporation supported, among other enterprises, a black doll company, Negro World newspaper, and Black Star Steamship Line. The latter operated three ships but it collapsed in 1921 reportedly due to mismanagement, fueling much criticism from rival organizations like the NAACP. In 1922 the United States indicted Garvey for mail fraud involving Black Star stock sales. His conviction, incarceration, and eventual deportation in 1925 began UNIA's decline. But it inspired ongoing black nationalist movements in America and the African diaspora.