The USS Niagara (SP-136), later designated PY-9, was a notable United States Navy patrol vessel that served from 1918 to 1931, with a history rooted in her origins as a luxurious steam yacht. Built in 1898 by Harlan and Hollingsworth in Wilmington, Delaware, Niagara was originally owned by Howard Gould, who commissioned her as a private vessel featuring a Welte Style 6 Concert Orchestrion, later replaced by a Welte Philharmonic Organ in 1912, highlighting her luxurious design and technological sophistication. Purchased by the U.S. Navy on 10 August 1917, Niagara was converted into an armed patrol yacht and commissioned at Tebo's Yacht Basin in Brooklyn on 16 April 1918. Her service began during World War I, where she played a vital role in escorting merchant convoys and conducting patrols across the Atlantic and Caribbean. Notably, Niagara departed New York on 21 May 1918 to escort a convoy to Bermuda and the Azores, arriving at Ponta Delgada on 12 August 1918. She continued her patrols in the Atlantic, including operations in the West Indies, where she assisted in rescuing the merchant sloop Gauntlet after a storm. Her service extended into the Caribbean, where she escorted ships such as the French cable ship Pouyer Quertier and visited multiple ports including Trinidad, Barbados, Martinique, and Puerto Rico. After the war, Niagara was involved in training and surveying missions, particularly in the Caribbean and Central America. Reclassified as PY-9 on 17 July 1920, she continued her survey work under the Navy Hydrographic Office, charting areas such as the Gulf of Venezuela and the coast of Central America. Decommissioned in 1922, she was recommissioned in 1924 for further survey missions, which lasted until her final cruise in 1930. Niagara was decommissioned on 3 March 1931 and struck from the Navy List later that year. She was sold for scrapping in 1933. Her storied career highlights her transition from a private luxury yacht to a versatile naval vessel, contributing significantly to maritime patrol, escort, and survey operations in the early 20th century.

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