USS Decatur, a 566-ton third-class sloop of war, was built at the New York Navy Yard. She was commissioned in March 1840 for a tour with the Brazil Squadron in the South Atlantic that lasted until February 1843. A cruise with the African Squadron followed in 1843-1845. Decatur's next active service was off eastern Mexico in 1847, during which her crew participated in wartime operations to attack Tuxpan and capture Tobasco. Early in 1848 the sloop returned to the anti-slave trade patrol off Africa, where she remained until November 1849.

During the first years of the 1850s, Decatur served along the Atlantic Coast and in the Caribbean. She was sent to the Pacific in 1854, enduring a difficult passage through the Strait of Magellan before arriving in Honolulu, Hawaii, in late March 1855. The next four years were spent cruising in the eastern Pacific from South America northwards. Decommissioned at the Mare Island Navy Yard, California, in June 1859, Decatur was thereafter laid up "in ordinary" except for Civil War duty as a defensive floating battery at San Francisco. She was sold in August 1865.

USS Decatur was named in honor of Commodore Stephen Decatur (1779-1820), one of the United States Navy's greatest heros and leaders of the first two decades of the 19th Century.