Subsequently, he served in the Mediterranean Sea on board Constitution, North Carolina, and Ohio,[1] receiving promotion to passed midshipman on 28 April 1832, and to lieutenant on 8 March 1837.

[2] In 1842 Gansevoort was serving as first lieutenant aboard the brig Somers, under the command of Alexander Slidell Mackenzie, when a planned mutiny was discovered, led by Midshipman Philip Spencer.

On the advice of Gansevoort and the other officers Mackenzie sentenced Spencer, Boatswain's Mate Samuel Cromwell and Seaman Elisha Small to death, and on 1 December the three men were hanged from the yardarm.

Promoted to commander on 14 September 1855,[2] Gansevoort landed seamen and marines from Decatur in January 1856 to defend Seattle, Washington Territory from Native Americans during the Puget Sound War.

[1][6] Between 1861 and 1863, during the Civil War, Gansevoort was in charge of ordnance at the Brooklyn Navy Yard,[1] receiving promotion to captain on 16 July 1862,[2] while helping fit out ships which had been acquired for blockade duty.