The U.S. Army began the construction of a military fort on the island in 1853 (California was part of Mexico until the Mexican- American war when the land was ceded to the U.S. in 1848). It was operated as a coastal fortification until it officially became a military prison in 1907. It continued operating as a military prison until 1933. At that time it was transferred to the Bureau of Prisons and became a U.S. Federal Penitentiary. The Federal Penitentiary was officially closed on March 21, 1963 by Robert Kennedy, the U.S. Attorney General. It then sat idle until it was occupied by the Indians Of All Tribes during their protest for 19 months in 1969-1971. After that it sat idle again until it was turned over to the National Park Service in 1972 and was first opened to the public in October, 1973.
Alcatraz was a military base from 1847 to 1933. And a prison for 29 years after that
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