R-2 (Submarine No. 79) was laid down 16 October 1917 by the Fore River Shipbuilding Co., Quincy, Mass.; launched 23 September 1918; sponsored by Mrs. Charles M. Cooke; and commissioned at Boston 24 January 1919, Lt. Comdr. Charles Maynard Cooke, Jr., in command.
After acceptance trails in Cape Cod Bay, R-2 was assigned to Submarine Division 9 of the Atlantic Fleet and based at New London. She sailed 4 December 1919 for Norfolk and winter division maneuvers in the Gulf of Mexico. Returning to New London 28 May, she joined R-1 (SS-78) and R-3 (SS-80) for 4 months of summer exercises off southern New England. Designated SS-79 in July, R-2 headed for Norfolk 13 September 1920 for an overhaul.
R-2 was transferred to the Pacific 14 April 1921, transited the Panama Canal 28 May, and arrived 30 June at her new base, San Pedro, Calif. She took part in fleet exercises off Central America from 5 February to 6 April 1923. Returning to San Pedro 10 April, R-2 was ordered to Hawaii on 16 July with Division 9 and remained for 8 years developing submarine tactics with the Fleet. She made an endurance cruise to Midway Island in July and August 1924.
Leaving Pearl Harbor 12 December 1930, R-2 was reassigned to the Atlantic and arrived at New London via the Panama Canal 9 February 1931. She was attached to Division 4 and for the next 10 years served as a training ship for the Submarine School at New London and for the Yale University NROTC unit.
Assigned to Division 12 on 1 June 1941, R-2 departed New London 16 June and 6 days later arrived at Key West, her new homeport. Based there for the remainder of her career, she was attached to the Fleet Sonar School, and assigned periodically to defensive patrols in keeping with her limited operational capabilities, until the spring of 1945. Then, with the approach of German capitulation, she was ordered to Philadelphia for inactivation. Arriving 1 May, she was decommissioned 10 May and struck from the Navy list 2 June. She was sold to Rosoff Bros., New York, 28 September 1945; resold to the Northern Metals Co., Philadelphia, the following month; and scrapped in early 1946.