Alcatraz Island later invalidated the sale and paid Frémont nothing. Frémont and his heirs sued for compensation during protracted but unsuccessful legal battles that extended into the 1890s. Following the acquisition of California by the United States as a result of the Treaty of Guadalupe Hidalgo (1848) which ended the Mexican–American War, and the onset of the California Gold Rush the following year, the U.S. Army began studying the suitability of Alcatraz Island for the positioning of coastal batteries to protect the approaches to San Francisco Bay. In 1853, under the direction of Zealous B. Tower, the United States Army Corps of
Alcatraz Wharf and sank in deep water off the wharf in the early 1910s. Her crew of forty-two men escaped by jumping into the bay and swimming ashore. Seismic rehabilitation of the wharf occurred in the early 2000s. The retrofit to the existing wharf and its facilities consisted of concrete demolition, excavation, and installation of tiebacks. Reinforced steel and concrete were added to a new deck. Work was also done on the deteriorated piles under the wharf deck.David Finney is the youngest person to swim the South End Rowing Club Alcatraz Swim when he swam it in 2015 at ten years old.