Departing the United States Naval Submarine Base at New London/Groton, CT, on 27 November 1917, L-1 sailed for European waters to protect Allied shipping from German surface raider and submarine attacks. Following brief operations in the vicinity of the Azores, L-1 transited to the British Isles for patrol duty out of Bantry Bay, Ireland beginning in early February of 1918. The boat operated in British waters throughout the First World War to thwart the enemy German naval forces.

With the defeat of the Central Powers during November of 1918, L-1 departed Portland, England, on 3 January 1919, and transited to the Philadelphia Navy Yard arriving there on 1 February 1919.

From 1919 to 1922, L-1 operated along the Atlantic coast of the United States experimenting with new torpedoes and undersea detection equipment. The technological advances through tests performed by L-1 and her sister submarines during the post-World War I era added to the strength and quality of United States Navy submarines that contributed so much toward the defeat of Japan during the Second World War.

L-1 decommissioned at the Submarine Base at Hampton Roads, VA, on 7 April 1922. The submersible was sold to the Pottstown Steel Company on 31 July 1922 for subsequent scrapping.