(SP-136: dp. 2,690; l 282'0" b. 43'0"; dr. 17'0"; s. 12 k.; Cpl. 1651-a. 4 4", 2 'mg., 1 Y-gun)
Fort Niagara was captured from the British by American forces 28 November 1812.
The sixth Niagara (S. P. 136), a steam yacht built in 1898 by Harlan and Hollingsworth, Wilmington, Del., was purchased by the Navy 10 August 1917 from Howard Gould of New York City; converted into an armed patrol yacht; and commissioned in the Tebo's Yacht Basin, Brooklyn, N.Y., 16 April 1918, Comdr. E. B. Larimer in command.
Niagara departed New York 21 May as escort for a merchant convoy bound for Bermuda and the Azores. She arrived at Ponta Delgada, Azores, 12 August and departed 10 days later to join the American Patrol Detachment at Grassy Bay, Bermuda. On 5 September she stood out of the latter port to rescue and tow in the merchant sloop Gauntlet adrift after her sails had been carried away in a storm. On 14 September the patrol yacht sailed for Martinique, West Indies, to escort the French cable ship Pouyer Quertier, arriving Fort-de-France on the 19th. The two ships operated in the West Indies, visiting Trinidad, Barbados, Martinique, and Puerto Rico, until Niagara stood out from Port of Spain, Trinidad, 13 December for Charleston, S.C. She entered the New York Navy Yard 13 May 1919 for repairs before training out of New London and New York.
Niagara departed New York 25 September for Key West, then cruised off the coast of Mexico and between ports in Texas, Louisiana, and Florida. Other missions took her off Honduras, Guatemala, and Cuba. Reclassified PY-9 on 17 July 1920, she continued patrols in the Caribbean Sea as a unit of the special service squadron until decommissioning at Philadelphia 21 April 1922.
Niagara recommissioned 24 June 1924, Comdr. Paul P. Blackburn in command. She sailed 3 November to survey in the Caribbean under the direction of the Navy Hydrographic Office. She operated most of the next 8 years charting the Gulf of Venezuela and the coast of Central America.
Her last survey cruise ended when she returned to Philadelphia 17 October 1930. Niagara decommissioned 3 March 1931; and her name was struck from the Navy List 10 December 1931. She was sold for scrapping 13 September 1933 to the Northern Metal Co., Philadelphia, Pa.