USS Ammonoosuc (1864)

The first USS Ammonoosuc (later briefly renamed USS Iowa) was a 3,850‑ton wooden screw steam frigate of the Wampanoag class. Laid down during the American Civil War in early 1863 by the Boston Navy Yard and launched on 21 July 1864, she was designed for exceptional speed to counter Confederate commerce raiders and for potential use against Great Britain if they sided with the Confederacy during the American Civil War. She achieved a sustained speed of 17.11 knots (31.69 km/h; 19.69 mph) during sea trials in June 1868, briefly making her the fastest warship afloat. Despite this impressive performance, Ammonoosuc was never commissioned for active service. Her name was changed to USS Iowa on 15 May 1869, but it reverted to Ammonoosuc on 13 October 1870. The ship remained out of commission until her sale for scrap on 27 September 1883.

From the outbreak of the Civil War, the Lincoln Administration seemed to feel that the British Government's sympathies lay with the Confederacy. The Trent Affair further strained Anglo-American relations, and the terrible toll exacted from Union shipping by commerce raiding Confederate cruisers built in England forced the Union Navy to make contingency plans for what appeared to be an increasingly likely war with England.

With the Royal Navy considerably more powerful than its American counterpart, the United States Navy decided that—should open hostilities with Queen Victoria's empire break out—it would adopt its traditional strategy of preying on British merchant shipping. To prepare for such an eventuality, the Federal Navy Department embarked upon a program of developing very fast seagoing steamships capable of overtaking all ships they might pursue and of escaping from any they might wish to elude.

Ammonoosuc was one of these steamers. Her hull was designed by Benjamin Franklin Delano to hold a pair of extremely powerful engines to be built at New York City by the Morgan Iron Works according to plans drawn by Benjamin Franklin Isherwood for the screw frigate Wampanoag. These engines were not ready when Ammonoosuc was launched and the collapse of the Confederacy prompted a significant slowdown on the work as that all but eliminated the Navy's need for fast, new warships. The engines were finally finished late in 1867, and Ammonoosuc's hull was towed to New York City so that they might be installed.

In June 1868, under Commander William D. Whiting, the USS Ammonoosuc steamed from New York to Boston, Massachusetts. Despite navigating dense fog, she achieved a sustained speed of 17.11 knots while moving from Cape Cod to Fort Warren over a three hour period during her sea trials, briefly making her the fastest warship afloat. This impressive performance validated Isherwood’s innovative high-speed naval engineering concept, though concerns remained about the ship's structural integrity and seaworthiness at such speeds.

However, a significant portion of her hull was dedicated to her powerful engines and related machinery, leaving insufficient space for other essential operations. Consequently, the ship was never commissioned for active service and was instead laid up in the Boston Navy Yard. While in ordinary, Ammonoosuc was briefly renamed USS Iowa on 15 May 1869, a name that was reverted to Ammonoosuc on 13 October 1870.

She was sold at Boston on 27 September 1883 to the firm of Hubel and Porter, of Syracuse, New York.

• List of steam frigates of the United States Navy

•  This article incorporates text from the public domain Dictionary of American Naval Fighting Ships. The entry can be found here.
• "USS Ammonosuc (1868-1883)". Online Image Library. Naval Historical Center. 22 December 1998. Archived from the original on 5 January 2001. Retrieved 30 January 2008.