[2][3] She was purchased by the US Navy on 5 December 1940 and was sent to Bethlehem Steel Corp. in Boston, Massachusetts where she was converted into a patrol gunboat.

[2][3] St. Augustine was assigned to the 1st Naval District and operated out of Boston as a patrol ship until 1942.

[3][4] She was transferred to the Eastern Sea Frontier where she escorted convoys between New York City and various Caribbean ports.

[3][4] On the night of 6 January 1944, while leading a convoy from New York to Guantanamo Bay, Cuba, St. Augustine was accidentally rammed by merchant tanker Camas Meadows off the coast of Cape May, New Jersey.

[2][4] St. Augustine foundered within five minutes, and 115 of the 145 crewmembers on board were killed.