1865–1871 Nyack was assigned to the Navy's Pacific Squadron and set out for Valparaiso, Chile from New York on 22 July 1865. Her first stop was St. Thomas, Virgin Islands. On this first leg of the journey she burned fourteen tons of coal per day and averaged 8.5 knots. Nyack was at Rio de Janeiro, Brazil on 8 October 1865. She sailed from Montevideo, Uruguay, through the Strait of Magellan, and arrived in Valparaiso on 20 November 1865. 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. For example, she sailed from Valparaiso on 1 February 1866 for Callao, Peru. Here Nyack assisted the Peruvian Navy in towing its ironclad Loa off a shoal in the harbor. This might not have been seen as strictly neutral by Spain which was at war with its former colony at the time. Nyack went on to Panama City, Panama, arriving on 22 June 1866, but now under the command of Lieutenant Commander Austin Pendergast, Captain Newman having died of "brain fever" on 31 May 1866. 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. He was carried to safety in Chile aboard Nyack. In July 1868 Captain Pendergast was relieved by Lieutenant Commander Charles A. Babcock, who was, in turn relieved by Lieutenant Commander Thomas H. Eastman in late 1869. Nyack sailed to the Galápagos Islands in 1869 and did some surveying there, a track chart of which survives in the National Archives. 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. In January 1870, Nyack was ordered to support another surveying project, in this case an expedition to the Darien region of Panama. A U.S. force under Commander Thomas O. Selfridge explored the feasibility of an inter-oceanic canal at this location. Nyack was ordered to survey from the Gulf of San Miguel up the Savanna River, and the Bayamo River as far as the mouth of the Marmoni. She arrived on the Savanna on 13 April 1870. The ship surveyed 16 miles up the river