Upon being commissioned at the Boston [Mass.] Navy Yard on 29 September 1916, Lt. (j.g.) Augustine H. Gray in command, L-2 reported for duty with Division Five, Submarine Flotilla, Atlantic Fleet, on 2 October 1916. She continued fitting out and training out of Boston until 26 October, after which she then proceeded to the Torpedo Station at Newport, R.I., to take on her torpedo outfit (26-28 October). She then continued her shakedown training in the waters off New England and in Long Island Sound until 30 November. After taking a sick sailor to Newport, she set a course southward on 1 December, and after a pause off the Delaware Breakwater (5-7 December), L-2 continued on to the Norfolk Navy Yard, Portsmouth, Va. (8-18 December) and Key West, Fla. (23-30 December), undergoing overhaul at the latter, before arriving at Havana, Cuba, for liberty on 30 December.
L-2 spent the New Year’s holidays in port before departing Havana on 2 January 1917, arriving at Key West, later that same day. She remained until 22 January before departing for the Dry Tortugas, Fla. (22-26 January) en route to Pensacola, Fla. Reaching her destination on 28 January, she remained there until 17 February, when she shifted to Mobile, Ala. (17-21 February) before returning to Pensacola on the 21st. While the submarine was at Pensacola tensions with Germany increased with that nation’s resumption of unrestricted submarine warfare on 1 February. As a result, the annual Atlantic Fleet winter exercises in the waters off Cuba were cut short. After initial consolidation in Cuba’s Guacanayabo Bay, the fleet relocated to the sheltered waters of lower Chesapeake Bay by 31 March. Meanwhile, on 9 March, L-2 got underway for Force Exercise 7B and operated with Tallahassee (Monitor No. 9) and Columbia (Cruiser No. 12) in the waters of the Gulf of Mexico. With the fleet consolidating, L-2 departed Pensacola on 27 March. Transiting via Key West (30-31 March), she reached Hampton Roads, Va. (Base No. 3), on 5 April. The following day [6 April 1917], the U.S. declared war on Germany and L-2 shifted to the Norfolk Navy Yard. On 13 April, L-2 was alongside Bailey (Torpedo Boat No. 21) at Norfolk, engaged in minor structural work and repairs by the crew. She received orders to mobilize that same day. The submarine spent the remainder of the month undergoing modifications to engage in operations and conducted training. She shifted to the York River at Yorktown, Va. (Base No. 2) on 16 April. A fortnight later, L-2 cleared Yorktown at 8:00 a.m. on 30 April and proceeded with Bushnell (Submarine Tender No. 2), L-1 (Submarine No. 40), and L-3 (Submarine No. 42) in formation to join the fleet’s battleships at Tangier Sound, Va. (Base No. 1). L-2 departed York Spit, Va. on 4 May, bound for the Philadelphia [Pa.] Navy Yard in company with Bushnell, L-1, L-3, and L-4 (Submarine No. 43). All arrived without incident on 6 May.
In June 1917, Vice Adm. William S. Sims, Commander, U.S. Naval Forces in European Waters, cited British success in using submarines as submarine hunter-killers in antisubmarine warfare (ASW). The Allied boats, with their lower profiles, could approach U-boats more stealthily than larger surface patrol vessels. On 2 July, Adm. William S. Benson, Chief of Naval Operations, ordered the twelve most suitable submarines on the Atlantic coast be fitted out for duty in European waters. L-2 underwent extensive overhaul at Philadelphia to prepare her for distant service. With that work completed, she conducted exercises to test equipment on 14 November. As a result of the tests all unsatisfactory work was rectified (15-17 November) in advance of deployment.
L-2 in tow of Conestoga (Fleet Tug No. 54), in company with L-1; L-3; L-4; L-9 (Submarine No. 49); L-10 (Submarine No. 50); L-11 (Submarine No. 51); E-1 (Submarine No. 24); Bushnell (Capt. Thomas C. Hart, Commander, Submarine Flotilla embarked); and Fulton (Submarine Tender No. 1), cleared Philadelphia on 18 November 1917 and proceeded to New London, Conn. (Base No. 22), via Montauk Point, N.Y., and arrived on 20 November. She shifted to the Torpedo Station at Newport on 22 November and then returned that same day to New London. She conducted exercises in Long Island Sound with a simulated attack on Genesee (Fleet Tug No. 55). They departed on the 27th, bound for Melville, R.I., where they received lubricating and fuel oil and provisions. Clearing Melville on 4 December, Hart charted a direct course to the Azores, but his force ran into a gale which scattered the units and required them to pause and re-assemble at Bermuda (Base No. 24) on 13 December. L-2 continued on and reached Fayal Island, Azores on the 17th. She then proceeded into Ponta Delgada (Base No. 13), Azores, the next day. After provisioning, refueling, and conducting overhaul until 30 December, she stood out of the harbor and patrolled in relief of L-10 on the 31st. Though there were reports of U-boats having sunk a ship around the Azores, she conducted the patrol without incident. After conducting several patrols amidst the islands of the Azores archipelago in January 1918, L-2 and the other units of Division Five departed Ponta Delgada on 19 January and proceeded to Ireland.
L-2 arrived at Queenstown [Cobh] (Base No. 6), Ireland, on 27 January 1918, escorted by U.S. destroyers. She anchored that evening and then went alongside Bushnell, the next day. Though under the nominal command of Vice Adm. Sims, Hart’s U.S. submarines in Ireland, were subject to the authority of Vice Adm. Sir Lewis Bayly, RN, Commander-in-Chief, Coast of Ireland, and his submarine commander, Capt. Sir Martin E. Nasmith (later Dunbar-Nasmith), RN. Bayly initially ordered Hart to deploy only one of his submarines at a time at sea, and that Royal Navy officers were to always be informed of departures and returns. Their patrol area was also to be limited to seaward of the Fastnet Light, so as to keep clear of British patrols and to avoid potentially fatal “friendly-fire” incidents. The base at Queenstown, however, proved unsatisfactory for Lt. Cmdr. Harold M. Bemis’ Division Five, as it was also serving as the headquarters for the surface patrol forces. As a result, the U.S. submarines were relocated to a base at Berehaven [Castletownbere], Bantry Bay. In the ensuing days (6-16 February), the division trained in Bantry Bay conducting dives and tactical maneuvers under the charge of the commander of the Royal Navy’s Submarine Flotilla also based at Berehaven. U.S. submarine officers also trained with a “submarine attack war game” apparatus on board the submarine depot ship HMS Vulcan. In order to differentiate them from the British L-class submarines, the U.S. submarines were re-designated with the prefix “A” (American) and that letter was painted onto the fairwaters of the U.S. boats. The U.S. submarines’ patrols were to be based on eight-day rotations, there would be eight days on patrol and eight days in port for overhaul, re-provision, and rest in preparation for the next eight-day patrol. Now AL-2, in company with AL-4 and escorted by the sloop HMS Crocus, proceeded to Queenstown on 2 March. She then stood out of Base No. 6 on 18 March to conduct an ASW patrol. She continued to rotate in patrol duty, typically for eight days, with the other boats of the division in the succeeding months.
AL-2 got underway in Bantry Bay on 25 May 1918. After initially exercising with AL-11 she continued on to her patrol billet QB. While en route on 26 May, she sighted a ship resembling an enemy submarine on the surface bearing 300º about six miles distant. She raised speed and headed for the vessel and confirmed that she was a German U-boat. She then submerged and made her approach, but was unable to hear anything on her C tube or see her in the periscope. She then surfaced at 9:05 a.m. with negative contact. She then continued into her patrol sector. When at the western edge, she again sighted a conning tower at 3:42 p.m., three miles distant. She again submerged and made her approach. Having sighted it again through the periscope and heard it faintly through the C tube, she could not confirm that it was an enemy submarine. She then surfaced and having encountered two merchantmen, she hoisted her colors. Shortly thereafter, she again sighted a vessel dead ahead. Believing it to be a submarine she submerged to make her approach. Observing the vessel through the periscope, there was a consensus that it was an enemy submarine. The torpedo tubes were flooded, but as the identity of the target could not be confirmed they did not engage though they did maneuver to close range on a firing course. In the end, AL-2 broke contact and then surfaced to charge her batteries. A week later, while on patrol, she was sighted by surface patrol craft, which immediately maneuvered for an attack. The submarine fired a night grenade and then there was an exchange of recognition signals that forestalled an attack. Later that day, a British seaplane passed above and the submarine again deployed a recognition signal to order to forestall taking friendly fire. Continuing on patrol, a submarine was detected surfacing and AL-2 maneuvered accordingly, but no further positive contact was gained.
AL-2 was on patrol en route to a return to Berehaven during the morning of 10 July 1918, when she encountered Parker (Destroyer No. 48) and McCall (Destroyer No. 28) heading toward her. She made a challenge with her blinker and fired smoke bombs as recognition signals, but received no reply. One of the destroyers then opened fire on her at 6,000 yards. The submarine fired five additional smoke bombs and continued signaling with her Aldis lamp. The destroyer fired a total of five rounds, with no hits, and finally ceased firing after recognizing the signals and closing to a distance of 2,000 yards. The submarine continued in toward Berehaven. Later, at 5:55 p.m., about 15 miles south of the Fastnet Light, a lookout sighted a dark object three points off the starboard bow which was believed to be a nun buoy. The boat then changed course and continued and the object disappeared. At 6:30 p.m., AL-2 reported that a torpedo from an enemy submarine was fired at her and detonated 200 feet from her engine room. The periscope of the enemy was plainly visible on the starboard quarter about 80 yards distant. Lt. Paul Foster, the submarine’s commanding officer, went hard left rudder and made a crash dive to a depth of about 70 feet and listened for the enemy. Her logbook stated that “Submarines were plainly heard. Attempts made to chase one of them submerged. Heard several oscillator signals from one of the two enemy submarines. At 7:40 one submarine ahead died out of listening range southward; the one being chased stopped.” Her subsequent report stated that Foster dived to ram the enemy submarine after the torpedo explosion. The enemy was dead ahead and the chase began. Within minutes two submarines were reported, one to the northward fairly close. The one southward could only be heard, but it was this U-boat which AL-2 began to chase. Eventually losing the southerly submarine, AL-2 circled back over two hours in an attempt to re-establish contact with the U-boat initially detected to the north. Despite multiple stops of her engines to listen for the enemy, the U.S. submarine never re-established contact. She then surfaced and submitted her report of the contact via wireless to Bushnell at Bantry Bay. AL-2 reported hearing an explosion from an unknown source and believed that it might have destroyed the U-boat. After this engagement, AL-2 finished her patrol and returned to Berehaven the following day.
The following month, on 25 August 1918, AL-2 was again underway on patrol when she reported a likely encounter with a submarine. She reported hearing the submarine, but given the rough seas running at that time, she dared not attempt to make a visual contact with her periscope as her tower would be visible in the troughs. She also reported a possible contact three days later, but given that her batteries were almost expended, she was unable to give chase. AL-2, on 24 September 1918 cleared Berehaven bound for Devonport, England, to train with U.S. submarine chasers based at Plymouth, England. The end of hostilities on 11 November, found AL-2 still based from Plymouth.
AL-2 departed Plymouth for the dockyard at Portland, England, on 10 December 1918, making arrival the next day. She remained at Portland through the end of the year, preparing for her homebound transit.
AL-2 stood out of Portland to return to the U.S. on 3 January 1919. Proceeding via the Azores, she reached Ponta Delgada on 10 January and secured alongside Yarnall (Destroyer No. 143) before later shifting to Bushnell. She cleared Ponta Delgada on 14 January bound for Bermuda (Base No. 24). She reached His Majesty’s Dockyard, Ireland Island, Bermuda, on 26 January and secured alongside Bushnell. After refueling and provisioning, she stood out on 28 January and headed for the Philadelphia Navy Yard, where she arrived on 1 February.
After her return to the U.S., the submarine underwent post-deployment overhaul and repairs at Philadelphia. When returned to operational duty, she experimented with torpedo and undersea detection techniques and equipment along the Atlantic coast. Again known as L-2, the submarine was re-designated as SS-41 as part of a Navy-wide administrative re-organization. She went in to the Norfolk Navy Yard in August 1920 and then cleared on 15 September. On 16 November, L-2 received orders transferring her homeport and that of L-1 (SS-40), L-3 (SS-42), L-4 (SS-43), L-9 (SS-49), L-10 (SS-50), L-11 (SS-51), and M-1 (SS-47) from Submarine Base, headquartered afloat in Eagle 17 (PE-17), Hampton Roads, Va., to the Submarine Repair Division, Philadelphia Navy Yard. The Submarine Repair Division was subsequently abolished on 26 March 1921, and the submarines were assigned to Submarine Division Three in an inactive status.
L-2 was brought in to the Philadelphia Navy Yard under tow of the tug Kalmia (AT-23) on 3 February 1921. The submarine was then ordered to transfer to Submarine Base, Eagle 33 (PE-33), New London, Conn. for the installation of new main engines from N-class submarines on 23 August 1921. She later arrived under tow of Kalmia at New London on 21 September. L-2 was considered to be in commission in reserve effective 5 December 1921. As of 18 April 1922, L-2, along with L-3, L-9, and L-11, were considered to be in good operating condition as second line submarines. Despite this assessment, L-2 was placed in reduced commission at New London, on 1 May 1922 along with L-3, L-9, L-11, N-1 (SS-53), N-2 (SS-54), and N-3 (SS-55). Just over a week later, on 9 May, L-2 was assigned to Submarine Division Zero at New London.
On 12 January 1923, she cleared New London, bound for the Portsmouth Navy Yard, Kittery, Maine. Arriving on 14 January, she docked until 9 March, when she cleared the yard to make her return up the Thames River to New London the next day. She the departed New London and proceeded to the Submarine Base at Hampton Roads, Va., reaching there on the 15th. L-2 decommissioned at Hampton Roads on 4 May 1923. Eleven months later, on 4 April 1924, the Navy issued orders directing that L-2 and 25 other submarines be towed to the Philadelphia Navy Yard. She went into dry dock (3 June-17 July), then on 18 August, was taken under tow by the minesweeper Owl (AM-2) and arrived at the Philadelphia Navy Yard on 19 August.
Stricken from the Navy list on 18 December 1930, L-2 was sold to the Pottstown Steel Co., Douglassville, Pa., on 25 June 1933 and scrapped in accordance with the terms of the London Treaty on 28 November.