America, a heavy screw tugboat built at Philadelphia, in 1864, was purchased by the Union Navy December 9, 1864, from John W. Lynn; renamed Periwinkle; and commissioned early in January 1865, acting Master Henry C. Macy in command.

The two-masted, schooner-rigged, white oak tug joined the Potomac Flotilla on January 15, 1865, as a gunboat, operating primarily in the Rappahannock River.

In mid-March, a fleet of oyster schooners operating in the area was threatened by a Confederate enemy force, and Periwinkle with USS Morse, blockaded the mouths of the Rappahannock and Piankatank rivers to protect them.

The Flotilla also interrupted contraband business between lower Maryland and Virginia, and cleared the rivers of mines, and fought guerillas ashore.

Renamed USS Polaris in early-1871, she arrived at the New York Navy Yard on June 9 to complete loading of stores and provisions for the expedition.