CSS Teaser had been the aging Georgetown, D.C. tugboat York River until the beginning of the American Civil War, when she was taken into the Confederate States Navy and took part in the famous Battle of Hampton Roads.

With Lieutenant William A. Webb, CSN, in command, she took an active part in the Battle of Hampton Roads on March 8–March 9, 1862, acting as tender to CSS Virginia.

While engaging USS Maratanza at Haxall's on the James on July 4, 1862, a Union shell blew up Teaser's boiler and forced her crew to abandon ship.

On October 19, while operating in the vicinity of Piney Point in St. Mary's County, Maryland, she captured two smugglers and their boat as they were nearing the exit of Herring Creek and preparing to cross the river to Virginia.

In April 1863, Teaser left the Potomac for duty with Acting Rear Admiral Samuel Phillips Lee's North Atlantic Blockading Squadron at Hampton Roads.

During the night of October 7, Teaser and another flotilla ship (extant records do not identify her companion) noticed signalling between Mathias Point, Virginia, and the Maryland shore.

The two ships shelled the woods at Mathias Point, but took no action against the signallers on the Maryland shore other than to urge upon the United States Army's district provost marshal the necessity of constant vigilance.

At 5:00 A.M. on April 13, the five ships cleared the St. Mary's River in company with the Army's steamer USAT Long Branch with a battalion of soldiers under the command of General Edward W. Hinks.

A contingent of Confederate cavalry appeared on the southern bank of the Machodoc, but retired when Teaser and Anacostia sent four armed boat crews ashore.

On this occasion, the Union forces needed her guns to help defend strategic bridges across the rivers at the head of Chesapeake Bay near Baltimore, Maryland, against Lieutenant General Jubal A.

Teaser departed the northern reaches of the Chesapeake and reported back to the Potomac Flotilla at St. Inigoes, Virginia, on the St. Mary's River in late afternoon on April 14.

For the remainder of the war, Teaser and her flotilla-mates plied the Potomac and contributed to the gradual economic strangulation which brought the South to its knees by April 1865.