Myrtle was built as a private motorboat of the same name in 1915 by T. B. Hayman at Elizabeth City, North Carolina. On 26 August 1918, the 5th Naval District inspected her at Norfolk, Virginia, for possible naval service, and on 16 October 1918, the U.S. Navy leased her from her owner, A. S. Rascol of Windsor, North Carolina, for use as a section patrol boat during World War I. She was commissioned as USS Myrtle (SP-3289). Assigned to the 5th Naval District, Myrtle carried out patrol and dispatch duties in the Norfolk area for the rest of 1918.