Dreadnought was built as a private fast "runabout" motorboat of the same name by R. Bigelow at Monument Beach, Massachusetts, in either 1916 or 1917. On 17 May 1917, the U.S. Navy acquired her from her owner, Eldon B. Keith of Brockton, Massachusetts, for use as a section patrol boat during World War I. She was commissioned as USS Dreadnought (SP-584) on 20 October 1917. Assigned to the 5th Naval District, Dreadnought carried out patrol duties there for the rest of World War I. In 1918, she was renamed USS SP-584. SP-584 was returned to her owner on 6 June 1919.