General Dynamics Electric Boat is today the leading contractor for the U.S. Armed Forces for the construction of submarines as well as upgrades, overhauls and maintenance of the existing fleet..  They are based at Groton, Connecticut and their main building facility is Quonset Point in Rhode Island.

It was founded on 1899 as The Electric Boat Company by Isaac Rice for the purpose of the construction of John Phillip Holland's submersible vessel (The Holland) which was incorporated into the U.S. Navy in the year 1900, beginning in this mode the U.S. Submarine Forces.  During WWI, the company was asked for the commission of 85 submarines and one of its subsidiaries got the task of building submarine chasers.

After WWII, Electric Boat pursued a number of non military projects and in 1954,  the world first nuclear powered submarine, The Nautilus was built in only three years.  Most of the leading submarine classes in the U.S. Navy were designed or built by Electric Boat:  Los Angeles fast attack class, the Tridents, the Seawolf and the Virginia, the Navy's newest line of submarines.

Today, the process of building a submarine can take up to six years from the contract acceptance to the final commissioning of the new ship.  It takes a lot of research and testing, even for the construction of existing models.  Not only they build for the U.S. Navy, they are also contracted by foreign governments and private entities.

Electric Boat is part of General Dynamics, one of the leading companies in the manufacture of naval and aviation equipment, as well as other mission critical systems.

Main Source: The Electric Boat Web Site.