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
Occupation of Alcatraz Movement noted from their visit to the occupation that the demonstration garnered national attention, while those involved faced no punitive action. When AIM members seized the Mayflower II on Thanksgiving, 1970, the Occupation of Alcatraz was noted as "the symbol of a newly awakened desire among Indians for unity and authority in a white world." The occupation of Alcatraz Island served as a strong symbol and uniting force for indigenous peoples everywhere because of the importance the island held in their ancestors' lives. Indians traveled to Alcatraz about 10,000 years before the Europeans even entered the Bay area. Over the