|USS Lewes off Lorient, France, circa 1918. From NavSource Online|
In May of 1917, she was purchased by the US Navy and Commissioned as the USS City of Lewes. In July, she was recommissioned as simply USS Lewes. In August and September the Lewes sailed across the Atlantic for the port city of Brest, in France, as part of a squadron described in On the coast of France: the story of the United States naval forces in French waters (Joseph Husband, A.C. McClurg & co., 1919):
The next squadron of the patrol force, Captain TP Magruder USN in command, reached Brest on the afternoon of September 18, and consisted of the yacht USS Wakiva, the supply ship USS Bath, and the trawlers USS Anderton, USS Lewes, USS Courtney, USS McNeal, USS Cahill, USS James, USS Rehoboth, USS Douglas, USS Hinton, and USS Bauman. With these also arrived six 110-foot patrol vessels under the French flag. Due to the construction of the trawlers, which was soon proved to be entirely unsuited for the hard sea service required, they were withdrawn after a few weeks from escort duty and fitted for mine-sweeping.The USS Rehoboth was a sister ship of the Lewes, having also been built in Milford and bought into the service. And I've found references to a USS Henlopen, built by W.G. Abbott, as well.
According to the US Naval Historical Center, the Lewes spent most of her time as a mine-sweeper, keeping the coast of France free from floating German mines, an effort that continued int 1919 after the end of the war. She was decommissioned in September of 1919 and sold.