The destructive foray of the Confederate ironclad ram CSS Albemarle from the Roanoke River into Albemarle Sound, North Carolina, on 17 April and her reappearance on 5 May—the day Grant's offensives began—increased Union anxiety over the possibility that the Confederate squadron at Richmond might descend the James, wrest control of that vital stream from the Union flotilla, and wreck Butler's transports and supply ships, stranding his troops in hostile territory where they would be at the mercy of Southern soldiers. To prevent such an eventuality, Welles sent several warships, formerly ordered to the Gulf of Mexico, to Hampton Roads, Virginia, to reinforce the James River Flotilla.
Althea was one of these ships. While the date of her departure from New York City is not known, the tug was said to be serving on the James in the dispatch dated 17 June 1864 which reported the locations of the ships of the North Atlantic Blockading Squadron. She had been fitted out with a spar torpedo to be used in attacking any Confederate ironclad which might appear and she was prepared to act as a ram should an opportunity for such employment arise. The tug also served as a tender to Union ironclads in the James.
Gulf service
Late in July, the situation in that river seemed stable enough to permit the Union warships borrowed from Farragut to move on to the Gulf of Mexico. Repaired and prepared for sea by the Norfolk Navy Yard, Althea departed Hampton Roads in company with three other tugs on the 26th and reached Mobile Bay on 5 August, the day of Farragut's great victory there.
Too late to participate in the historic Battle of Mobile Bay, Althea busied herself in ensuing months supporting Farragut's combatant ships as they joined Army forces in operations against the city of Mobile, Alabama. On 12 April, the day Mobile finally surrendered, Althea struck a torpedo (naval mine) in the Blakeley River and sank while returning from a run up that stream in which she had dragged primitive sweep gear in an effort to clear the channels of explosive devices. Two members of her crew were killed in the accident, and three others—including the tug's commanding officer, Acting Ensign Frederick A. G. Bacon—were wounded.
Raised and repaired after the Confederate collapse, Althea was recommissioned at Mobile on 7 November 1865. She carried out towing chores and performed other varied services there, at Pensacola, Florida, and at Key West, Florida, until—towing the monitor USS Sangamon – she departed the latter port on 10 April 1866. After reaching the Philadelphia Navy Yard on the 18th, she was decommissioned on 25 April 1866 and sold at auction on 8 December 1866.
Commercial service
Redocumented Martin Kalbfleisch on 10 January 1868, she served as a merchant tug until 1896.
