In 1821, the SF area became part of Mexico. Mexico ceded the territory to the US in 1848. The Gold Rush raised the population from 1,000 in 1848 to 25,000 in 1849. Crews on arriving vessels rushed off to gold fields, leaving behind a forest of masts of 500+ ships in SF harbor. Some were used as storeships, saloons, and hotels; many were left to rot and some were sunk to establish title to the underwater lot.
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