The USS California (ACR-6), later renamed San Diego, was a Pennsylvania-class armored cruiser constructed for the United States Navy. Launched on April 28, 1904, by Union Iron Works in San Francisco, she was commissioned on August 1, 1907. The cruiser featured heavy armor and armament typical of the Pennsylvania class, designed to serve as a formidable surface combatant and flagship. Initially assigned to the Pacific Fleet’s 2nd Division, California participated in various training exercises, including the 1908 Naval Review in San Francisco. Her early service included cruises to Hawaii and Samoa, as well as operations along the U.S. West Coast. In 1912, she was deployed to the Asiatic Station, representing American interests in East Asia, before returning home later that year. During her operations along the coast of Central America and Mexico, she was involved in protecting American lives and property during regional political disturbances, notably suffering the loss of two crew members who were shot during a confrontation in Mexico. On September 1, 1914, she was renamed San Diego to free her original name for a battleship. She served intermittently as the flagship of the Pacific Fleet until a boiler explosion in January 1915 placed her in reduced commission at Mare Island Navy Yard. During this incident, Ensign Robert Cary and Fireman Second Class Telesforo Trinidad performed actions that earned them the Medal of Honor. After repairs, she served as a popular attraction during the Panama–California Exposition. Reactivated for World War I, San Diego was commissioned fully on April 7, 1917. She served primarily as a convoy escort in the North Atlantic, operating out of Tompkinsville, New York, and Halifax, Nova Scotia, safeguarding vessels from submarine threats. On July 19, 1918, while en route from Portsmouth to New York, San Diego was struck by a violent explosion on her port side, leading to her sinking in just 28 minutes. Six crew members lost their lives. Though initially believed to be torpedoed, later investigations and underwater studies indicated she was likely sunk by a mine, possibly laid by the German U-156 submarine. Her wreck now lies inverted in 110 feet of water off Long Island, becoming a popular scuba diving site known as the "Lobster Hotel" due to its abundant marine life. The shipwreck is listed on the National Register of Historic Places and remains a significant maritime artifact, representing early 20th-century naval design and the perils faced during wartime convoy operations.

This description has been generated using GPT-4.1-NANO based on the Vessel's wikidata information and then modified by ShipIndex.org staff.