(ScGbt: t. 507; 1. 158'4"; b. 28'0"; dph. 12'0"; dr. 10'6"; s. 111/2 k., cpl. 84; a. 1 11" D. sb., 1 20-par. P.r., 2 24-par. how.)
The first Seneca-a wooden-hulled "ninety day gunboat" built at New York City by J. Simonson-was launched on 27 August 1861, and commissioned at the New York Navy Yard on 14 October 1861, Lt. Daniel Ammen in command.
On 5 November 1861, Seneca and three other Federal Union gunboats engaged and dispersed a Confederate squadron near Port Royal, S.C.; two days later, she took part in the capture of Port Royal, which proved to be an invaluable Union naval base throughout the remainder of the Civil War. From the 9th to the 12th she took part in the expedition which took possession of Beaufort, S.C. On the 5th of December, she participated in the operations about Tybee Sound to help seal off Savannah, Ga. The next day, she was in sight during the capture of schooner, Cheshire, entitling her crew to share in prize money.
From January 1862 to January 1863, Seneca's area of operations extended from Wilmington, North Carolina, to Florida. On 27 January 1863, she took part in the attack on Fort MeAllister, Gal; and, on 1 February, she participated in a second attack. On 28 February in the Ogeechee River, she supported Montauk in the destruction of privateer, Rattlesnake, the former Confederate warship, Nashville. In July 1863, she was one of the vessels in the attack on Fort Wagner. She later returned via Port Royal to the New York Navy Yard where she was decommissioned on 15 January 1864.
She was recommissioned on 3 October 1864, Comdr. George E. Belknap in command, and was assigned to the North Atlantic Blockading Squadron. On 24 and 25 December 1864, Seneca took part in the abortive attack on Fort Fisher, and, between 13 and 15 January 1865, she participated in the successful second attack which finally captured that Southern coastal stronghold and doomed Wilmington, closing the Confederacy's last major seaport. On 17 February, she was in the force which attacked Fort Anderson and captured it two days later.
At the end of the war, Seneca returned to Norfolk Cva., where she was decommissioned on 24 June 1865. The ship was sold on 10 September 1868 at Norfolk to Purvis and Company.