(SeGbt.: t. 593; 1. 179'6"; b. 30'6", dr. 11'6", s. 9.5 k.; cpl. 127; a. 1 100-pdr., 1 30-pdr. P.r., 6 32-pdrs.,1 24-pdr. how., 1 12-pdr. r., 1 32-pdr.sb.)
The first Saco was launched on 28 August 1863 by the Boston Navy Yard, Boston, Mass., and commissioned there on 11 July 1864, Lt. Comdr. John G. Walker in command.
Throughout the autumn and into the winter of 1864 the new gunboat cruised along the Atlantic coast ranging from Halifax, Nova Scotia, to Wilmington, N.C., in search of Confederate raiders and blockade runners. However, since boiler and engine trouble hampered the ship during much of this service, Saco was decommissioned at the Washington Navy Yard on 27 January 1865 for repairs.
The Civil War ended while work on the gunboat was still in progress, so Saco remained in ordinary during the demobilization program which followed the end of the fighting. She was recommissioned on 10 June 1866 and operated along the Atlantic coast, in the Caribbean, and in the Gulf of Mexico. She also served as a training ship at the Naval Academy before decommissioning at Norfolk on 17 December 1868.
Recommissioned on 22 July 1870, Saco departed Hampton Roads on 6 August and steamed to European waters. She cruised in the Mediterranean for over a year before getting underway from Naples on 14 December 1871 and heading for the Suez Canal and the Far East.
After arriving at Shanghai on 6 May 1872, Saco remained in Asiatic waters until returning to the United States in 1876. She was decommissioned at the Mare Island Navy Yard on 13 July 1876 and remained in ordinary there until she was sold to William E. Mighell on 20 November 1883.