Commissioned on August 6, 1988, and built by General Dynamics Electric Boat, USS San Juan measured 110.3 meters in length with a 6,197-long-ton submerged displacement, powered by an S6G nuclear reactor supplying 33,500 shaft horsepower. Armed with four 533 mm torpedo tubes and 12 Tomahawk vertical launch cells, the boat completed its final 37,600-nautical-mile deployment in June 2023 before transitioning into stand-down ahead of its final decommissioning.

On August 6, 2026, the U.S. Navy decommissioned the USS San Juan (SSN-751) at the U.S. Naval Undersea Museum in Keyport, Washington, exactly 38 years after the submarine was commissioned on August 6, 1988. The retirement removed the first Improved Los Angeles-class nuclear-powered attack submarine from the fleet and ended the career of the boat that established the 688i configuration subsequently used from SSN-752 through SSN-773. USS San Juan completed its final operational deployment on June 6, 2023, after five-and-a-half months in the U.S. Sixth Fleet area, departed Naval Submarine Base New London for the Pacific on August 21, 2023, reached Naval Base Kitsap-Bremerton on September 20, and entered Reserve, Stand Down status on August 12, 2024.

The timing of the retirement is operationally significant because the U.S. Navy is now removing Los Angeles-class submarines at a rate that exceeds Virginia-class deliveries, with the U.S. attack submarine (SSN) inventory projected to decline from roughly 49 to 50 boats in 2025 toward 46 to 47 near 2030, compared with a long-term requirement of 66 SSNs. General Dynamics Electric Boat received the contract for the USS San Juan on November 30, 1982. The keel was laid at Groton, Connecticut, on August 9, 1985; the submarine was launched on December 6, 1986, and commissioning followed on August 6, 1988, under Cmdr. Charles Young.

By then, the U.S. Navy had already divided the Los Angeles-class into three production groups: 31 Flight I submarines from USS Los Angeles (SSN-688) through USS Providence (SSN-718), eight Flight II submarines from USS Pittsburgh (SSN-719) through USS Newport News (SSN-750), and the final 23 Flight III boats from USS San Juan (SSN-751) through USS Cheyenne (SSN-773). Flight II had introduced a separate battery of 12 vertical launch tubes for Tomahawk missiles, allowing cruise missiles to be fired without using the four bow torpedo tubes, but Flight III (also known as 688i or Improved Los Angeles-class) addressed a different set of problems generated by the improving Soviet submarine force.

The USS San Juan moved the diving planes from the sail to retractable positions on the bow, received a reinforced sail designed to penetrate Arctic ice, incorporated additional noise-reduction measures, added mine-laying capability, and introduced the AN/BSY-1 combat system. The changes were intended to improve the ability to trail quieter Soviet attack submarines, including the Sierra and Akula classes, and to operate beneath the Arctic ice in areas associated with Soviet ballistic missile submarine patrols. That mission requirement explains why the USS San Juan measured 110.3 m long, 10 m in beam, and 9.4 m in draft. Additionally, its displacement was 5,790 long tons in the lighter condition and 6,197 long tons at full displacement. Propulsion came from one General Electric S6G pressurized-water reactor using a D2W core rated at 165 MW thermal.

That reactor supplied steam to two main propulsion turbines producing 33,500 shaft horsepower through a single shaft, while a 325 hp secondary propulsion motor could provide limited movement if the main propulsion system was unavailable. The Los Angeles-class official submerged speed exceeded 25 knots, while higher maximum figures remained classified. The class had an endurance commonly listed at about 90 days, with nuclear propulsion removing fuel endurance as the principal limitation and shifting operational endurance toward food, maintenance, crew, and mission requirements. USS San Juan normally carried 12 officers and 98 enlisted personnel in its listed configuration. The compact internal volume imposed by a 110.3 m hull meant propulsion machinery, reactor systems, sonar processing spaces, torpedo-room storage, command spaces, crew accommodation, and auxiliary systems all had to be contained within two principal watertight compartments, a layout that remained fundamentally rooted in Cold War attack submarine design.

The USS San Juan had four 533 mm, 21-inch torpedo tubes and 12 dedicated vertical launch tubes located forward of the sail. The torpedo tubes could employ Mk 48 ADCAP heavyweight torpedoes for submarine and surface targets, UGM-84 Harpoon anti-ship missiles, Tomahawk missiles when required, and submarine-launched mines including the Mk 67 mobile mine. The last 31 Los Angeles-class submarines, comprising Flight II and Flight III, added the 12-tube Tomahawk vertical launch system to the internal torpedo room load. Therefore, a 688i submarine could begin a deployment with a 12-missile land attack battery already segregated from the weapons needed for anti-submarine warfare, rather than filling part of its torpedo room capacity with cruise missiles. A submarine tasked with strike missions could therefore preserve Mk 48 availability and avoid tying up torpedo tubes during the initial launch sequence.

The arrangement became increasingly relevant after the Cold War because Los Angeles-class boats shifted from an overwhelmingly submarine-hunting mission toward a combination of anti-submarine warfare, anti-surface warfare, intelligence collection and precision land attack. The USS San Juan demonstrated that transition operationally in March 2003 when it launched Tomahawk land attack missiles from the Red Sea in support of Operation Iraqi Freedom. The sensor and acoustic changes introduced by the USS San Juan were equally important because attack submarine effectiveness depends on detecting another submarine before being detected itself. The Flight III boats entered service with the AN/BSY-1 Submarine Advanced Combat System using the AN/BQQ-5E sensor configuration and more capable digital processing than earlier Los Angeles boats.

The wider AN/BQQ-5 family used a spherical bow sonar array containing 1,241 transducers, a conformal hull array with 104 to 156 hydrophones and multiple towed-array options, providing passive and active detection over different frequency bands and geometries. The 688i upgrade added improved electronics and acoustic isolation intended to reduce machinery-generated noise and improve the quality of passive sonar data reaching the processors. Lower self-noise mattered twice: it reduced the acoustic signal available to an adversary while simultaneously allowing the submarine`s own hydrophones to detect weaker contacts against a quieter internal background. The bow-plane arrangement also had an acoustic and hydrodynamic role in addition to its Arctic function.

Removing large diving planes from the sail improved flow around the upper hull and allowed the planes to be retracted when they were not required, while the strengthened sail could withstand ice-breaking loads. The USS San Juan validated the Arctic configuration in 1993 when it conducted the first through-ice surfacing by a 688i submarine. The result was a submarine designed to operate not only in the open Atlantic or Pacific but also beneath Arctic ice where access routes, acoustic propagation, and the inability to surface freely make submarine operations substantially more demanding. The USS San Juan then operated repeatedly in the Atlantic, Mediterranean, North Atlantic, Arctic, and Middle East, including deployments to the U.S. Fifth and Sixth Fleet areas.

Its March 2003 Tomahawk launches from the Red Sea were followed by continued deployments involving Bahrain, Jebel Ali in the United Arab Emirates, Souda Bay i