From: Dictionary of American Naval Fighting Ships, Vol. I p 26
Alert is an adjective meaning keenly watchful, vigilant.
The third Alert, an iron gunboat, was launched in September 1874 by John Roach and Son, Chester, Pa., and commissioned the following year, Commander W. T. Sampson in command.
Between 1876 and 1886 Alert completed three tours on the Asiatic Station. Out of commission at San Francisco until January 1887, she then joined the Pacific Station. She cruised in South American and Hawaiian waters until 22 February 1889 when she departed Honolulu for Apia, Samoa. Alert left Apia 31 May as escort for the damaged gunboat Nipsic and returned to Honolulu 2 August. She arrived at Mare Island 10 December and went out of commission 6 February 1890. Following her recommissioning 9 October 1890, she cruised on the Bering Sea seal patrol in June 1891 and then proceeded to the Asiatic Station, arriving at Yokohama, Japan, 10 October. She remained in the Far East until 15 August 1893 and returned to Mare Island 23 September where she again went out of commission 7 October 1893.
Recommissioned 4 AprIl 1894, Alert rejoined the Pacific Squadron and cruised along the west coast and in Central American waters. Between 2 and 4 May 1896 she landed men at Corinto, Nicaragua, to protect American citizens and property and repeated the operation at San Juan del Sur, Nicaragua, 7--8 February 1898.
Alert lay out of commission at Mare Island Navy Yard 4 June 1898--11 May 1901. She then cruised along the west coast as a training vessel until 21 November 1903. Decommissioned 10 December 1903 at Mare Island, she was loaned to the California Naval Militia as a training vessel 1 June 1906. After her return to the Navy 27 February 1910, she lay unused at Mare Island until starting conversion to a submarine tender in 1911.
Recommissioned as a submarine tender 1 July 1912, she served in west coast and Hawaiian waters with the Torpedo Flotilla, Pacific Fleet, until 1917. After serving briefly as a base and repair ship at Bermuda during early 1918, Alert returned to the Pacific as a tender at the Submarine Base, San Pedro, Calif. She was decommissioned at Mare Island 9 March 1922 and sold 25 July 1922.