There aren't any coin mints in San Diego, CA. However, San Francisco, CA, is home to one of the most important U.S. Mint facilities. The mint was first established in 1854 to serve the gold mines of the California Gold Rush. Within the first year of its operation, the mint produced $4 million in gold coins. After twenty years, because of its increase in operation, it soon needed more space than its initial building and moved into a new one in 1894. In 1906, the mint suffered a fire from a massive earthquake and relocated to the third building in 1937.
Over the years, the San Francisco Mint has produced coins of numismatic quality. The most famous coins include the 1854-S Quarter Eagle, one of the rarest U.S. regular issue coinage, and the 1854-S Half Eagle, the second smallest gold coin, where only 268 pieces were minted, and only three are presently known to exist.
The U.S. Mint in San Francisco currently doesn't produce circulating coins. Instead, it mints commemorative coins and proof coin sets authorized by Congress.