High Quality Content by WIKIPEDIA articles! The occupation of Alcatraz was an occupation of Alcatraz Island by the group Indians of All Tribes (IAT). The occupation lasted for nineteen months, from November 20, 1969, to June 11, 1971, and was forcibly ended by the U.S. government. According to the IAT, the Treaty of Fort Laramie (1868) between the U.S. and the Sioux returned all retired, abandoned or out-of-use federal land to the Native people from whom it was acquired. Since Alcatraz penitentiary had been closed on March 21, 1963 and the island had been declared surplus federal property in 1964, a number of Red Power activists felt the island qualified for a reclamation.