USS Nyack (/ˈnaɪ.æk/ ⓘ) was a wooden-hulled screw gunboat of the United States Navy that saw action in the American Civil War.

After the Civil war, she was transferred to the Pacific where she patrolled the west coast of South America until she was decommissioned in 1871.

They will all average eleven knots, are of light draught [sic] and will enter most of these southern harbors at high water.

[6] On 23 December 1864 she took on coal at Beaufort, South Carolina and then joined Admiral Porter's fleet in the Cape Fear River for the first assault on Fort Fisher.

Some histories of this battle place Nyack with the other gunboats of Porter's fleet in roughly the same position as she had in the first assault.

[7] Porter pushed up the Cape Fear River and began bombarding Fort Anderson on 17 February 1865.

Faced with the approach of 8,000 Union troops under the command of General John Schofield, the fort was evacuated that night.

[9] Nyack was assigned to the Navy's Pacific Squadron and set out for Valparaiso, Chile from New York on 22 July 1865.

[13][14] Over the next five years she cruised the coasts of Panama, Ecuador, Peru, and Chile, protecting American nationals and interests while seeking to avoid direct involvement in armed conflicts between Spain and her former colonies and in bouts of civil unrest.

[17] In January 1868, General Mariano Prado, President of Peru, was overthrown in a coup and sought refuge in the home of the United States ambassador.

[19][20] Nyack sailed to the Galápagos Islands in 1869 and did some surveying there, a track chart of which survives in the National Archives.

[21] Ecuadorean authorities viewed this trip with suspicion and began an investigation, as rumors circulated that Nyack was going to take possession of the islands for the United States.

[22][23] In January 1870, Nyack was ordered to support another surveying project, in this case an expedition to the Darien region of Panama.

This trip coincided with a great fire in the town and 60 men of the crew turned out to help fight the blaze.

[28] Captain Eastman was relieved of command there and placed under arrest on charges of debt and scandalous conduct.

[30] Nyack's boilers were damaged beyond repair, so she was forced to sail to Hawaii from Callao, a trip that took 45 days.

[32][33] Given Nyack's poor condition, however, the crew of Saginaw was embarked on Moses Taylor, which took them to San Francisco.