Founded in Detroit (1930), NOI is the largest body of unorthodox US black Muslims.

Relocating it to Chicago, Elijah Muhammad was imam from 1934 to 75. He oversaw construction of its home mosque and headquarters while preaching Islam, racial separatism, and black self-sufficiency. He converted Malcolm X in 1952, appointed him national spokesman, and opened dozens of mosques. Alongside the Clara Muhammad Schools (honoring his wife) and Muhammad Speaks, the official newspaper, NOI owned businesses, farms, and real estate in America and abroad. Muhammad rejected the civil rights movement and racial integration as “self-destruction, death, and nothing else.” Echoing that message, Malcolm X stressed black nationalism and armed self-defense before resigning in 1964.

By 1975 NOI had an estimated 120,000 members, 75 mosques, and assets of $40 million. Its prison education and antidrug programs transformed the lives of countless blacks. Rejecting its orthodox Islam affiliation, which followed Muhammad's death, Louis Farrakhan became imam of a walkout membership (20,000–50,000) in 1978. Restoring NOI's name and separatist and nationalist traditions, and publishing The Final Call, he has made NOI a controversial force in politics.