Atlanta Federal Penitentiary was a notorious part of the U.S. federal prison system. It housed several inmates best known for other supposed offenses but imprisoned for tax evasion, most notably Al Capone. Earlier, black nationalist Marcus Garvey had been imprisoned here for offenses allegedly growing out of his operation of the Universal Negro Improvement Association and its subsidiary, Black Star Lines. Later, baseball pitcher Denny McClain, the last pitcher to win thirty games in a season, served a sentence there for fraud. Following its closure as a regular prison, it was used as a detention center for Cuban refugees from the Mariel Boatlift who were found to be actual, rather than political, criminals or who were otherwise ineligible for release into American society.