The second USS Cyane was a sloop-of-war in the United States Navy during the Mexican–American War. Cyane was launched 2 December 1837 by Boston Navy Yard. She was commissioned in May 1838, Commander John Percival in command. She sailed 24 June 1838 for duty in the Mediterranean, returning to Norfolk, Virginia 16 May 1841. She cleared 1 November 1841 for the Pacific Squadron, returning 1 October 1844. Sailing again for the Pacific 10 August 1845 with Passed Midshipman Benjamin F. B. Hunter as her Sailing Master, Cyane served on the west coast during the Mexican War. On 7 July 1846 her commanding officer, Captain William Mervine, led a detachment of Marines and sailors from Commodore John D. Sloat's squadron ashore at Monterey, California, hoisting the American flag at the Customs House and claiming possession of the city and all of present-day California. On 26 July 1846 Lieutenant Colonel John C. Frémont's California Battalion boarded Cyane, now under the command of Commander Samuel Francis Du Pont, and the ship sailed for San Diego, California on 29 July 1846. She landed Marines at nearby La Playa, where they were warmly welcomed by the largely pro-American civilian population. The Marines took abandoned guns from Fort Guijarros and used them to lay siege to Old Town San Diego. A detachment of Marines and sailors from Cyane took possession of the town, raising the American flag. They were followed shortly by the Fremont volunteers and Cyanes detachment returned aboard to sail for San Blas where a landing party destroyed a Mexican battery 2 September. Entering the Gulf of California, Cyane seized La Paz and burned the small fleet at Guaymas. Within a month, she cleared the Gulf of hostile ships, destroying or capturing 30 vessels. In company with and , she captured the town of Mazatlán, Mexico, 11 November 1847. On 22 January 1848, she arrived off San José del Cabo to relieve the besieged garrison there. She landed a force of about 100 men who fought the final engagement and broke the Mexican siege. She returned to Norfolk 9 October 1848 to receive the congratulations of the Secretary of the Navy for her significant contributions to American victory in Mexico. Between 9 October 1851 and 24 June 1852 Cyane sailed in the Home Squadron, rejoining it 10 October 1852 to cruise constantly on the Atlantic coast and in the Caribbean from Nova Scotia to