Ellen was built as a civilian motorboat of the same name in 1917 by the Herreshoff Manufacturing Company at Bristol, Rhode Island, one of nine motorboats built to a common design for private owners in anticipation that their owners would make them available for naval service. The U.S. Navy acquired Ellen from her owner on 21 July 1917 for World War I service as a patrol vessel. She was commissioned on 2 August 1917 as USS Ellen (SP-1209). Ellen operated on section patrol duty for the rest of World War I. She was returned to her owner in April 1919.