In 1914, Garvey founded the Universal Negro Improvement Association (UNIA). Its goal: to promote self-reliance among African Americans and solidarity among blacks worldwide. Five years later, Garvey set up UNIA headquarters at Liberty Hall in Harlem. The message and the movement spread like wildfire: By the early 1920s, the UNIA had opened 700 branches across the country.

Garvey's "back to Africa" movement aimed to instill a sense of black pride—and to empower those of African descent to defy European domination and oppression. As contributions to his cause poured in from around the country, Garvey founded several black-owned enterprises. Foremost among them was the Black Star Line, a steamship company designed to foster trade and transport among blacks living in the United States, the Caribbean, and Africa.

In August 1920, hundreds of delegates from all over the globe packed Liberty Hall for UNIA's first International Convention of the Negro Peoples of the World. On August 3, some 25,000 people marched from Harlem to Madison Square Garden for a rally led by Garvey.

Garvey was frustrated not only with white hegemony but with the racism he encountered among fellow African Americans. He challenged the aristocratic ideals of so-called Talented Tenth leaders such as W. E. B. Du Bois—who, in Garvey's eyes, rejected their African heritage and discriminated against dark-skinned blacks. Du Bois, for his part, considered Garvey both a traitor and a dictator; the two leaders traded frequent rhetorical barbs and blows in public.

Like Du Bois, the U.S. government eyed Garvey's growing popularity with suspicion. In 1923, when the Justice Department convicted Garvey of mail fraud, it did so with the help of his detractors. After being imprisoned in 1925, Garvey was pardoned by President Calvin Coolidge and deported to Jamaica in 1927.