Following the US entry into World War One, Vestal was deployed to Queenstown where she provided services for ships of the American fleet. She stayed there for the duration of the war and beyond, finally returning in 1919.
In 1925 she underwent modification that changed her from a coal-powered ship to an oil-fired one. Soon thereafter, the submarine S-51 was rammed and sunk by the SS City of Rome and Vestal was called to help recover the submarine. Following the completion of recovery, Vestal was transferred to the Pacific fleet in 1927 and served there until the outbreak of war following the attack on Pearl Harbor on December 7th, 1941.
The Vestal was in Pearl Harbor the day of the attack, moored next to the USS Arizona (BB-39) when the attack started. Her vicinity to such a large target would have serious consequences as some of the large bombs meant for Arizona hit Vestal instead. With the explosion of the Arizona Vestal was cast adrift and purposefully beached to prevent her from sinking.
(more History to be written)