The Portsmouth Navy Yard is a United States Navy shipyard in Kittery on the southern boundary of Maine near the city of Portsmouth, New Hampshire. Founded in 1800, PNS is U.S. Navy's oldest continuously operating shipyard. Today, most of its work concerns the overhaul, repair, and modernization of submarines. he Portsmouth Naval Shipyard was established on June 12, 1800, during the administration of President John Adams. It sits on a cluster of conjoined islands called Seavey's Island in the Piscataqua River, whose swift tidal current prevents ice from blocking navigation to the Atlantic Ocean.
During World War I, the shipyard began constructing submarines, with L-8 being the first ever built by a U. S. navy yard. Meanwhile, the base continued to overhaul and repair surface vessels. Consequently, the workforce grew to nearly 5,000 civilians. It grew to almost 25,000 civilians in World War II when over 70 submarines were constructed at the yard, with a record of 4 launched in a single day. When the war ended, the shipyard became the Navy's center for submarine design and development. In 1953, Albacore revolutionized submarine design around the world with its teardrop hull and round cross-section. It is now a museum and tourist attraction in Portsmouth. Swordfish, the first nuclear-powered submarine built at the base, was launched in 1957. The last submarine built here was Sand Lance launched in 1969. Today the shipyard provides overhaul, refueling, and modernization work.
In the Modern Era, the PNS has undergone substantial upgrades such as the creation of a super flood basin, as well as new cranes and dewatering pumps for 2 of the shipyard's dry docks. The Portsmouth Navy yard as also announced the construction of a Virginia-class submarine waterfront support facility.