Vigilant was built as the private motorboat Marguerite II in 1909 by Henry L. Blatz at Philadelphia, Pennsylvania. She had been renamed Vigilant by the time the U.S. Navy acquired her from her owner, E. B. Smith of Philadelphia, in 1917 for use as a section patrol vessel during World War I. She was commissioned as USS Vigilant (SP-406) on 19 May 1917 at the Philadelphia Navy Yard with Ensign John B. Yarnall, USNRF, in command. In 1918, Vigilant was renamed USS SP-406, apparently to avoid confusion with the tug USS Vigilant, which was in commission at the same time.