USS Joseph P. Kennedy, Jr. (DD-850) is a World War II Gearing class destroyer. She was built by the Bethlehem Steel Company at Quincy, Massachusetts. She was launched on July 26, 1945, and commissioned on December 15, 1945.
The Gearing class destroyers represented the ultimate development in wartime US destroyer design. They were Summers lengthened by 14 feet to increase fuel capacity and, at the same time, reduce wavemaking resistance and so restore some speed. They were sometimes referred to as "long hulled Summers."  Otherwise they were similiar to the previously designed Allen M. Sumner class of destroyers.
In 1961 USS Joseph P. Kennedy, Jr. was extensively modernized into an ASW (anti-submarine warfare) destroyer. The torpedoes were replaced by guided missile equipment (ASROC launchers) and a remote control Dash Helicopter (no longer extant) was installed on the after deck. 
USS Joesph P. Kennedy, Jr. is in good condition and, although modified, retains much of her World War II integrity.
Role of the Destroyer in World War II
The destroyer had its origin in the late-19th century with the development of the first self-propelled torpedo. Navies quickly developed small fast torpedo boats designed to attack and sink larger battleships and cruisers. As a counter against torpedo boats, navies built a slightly larger ship, armed with torpedoes and heavier guns. These 900-ton ships were known as torpedo boat destroyers, World War I showed these ships suited to protecting larger ships against surface, submarine, and air attack. Also, they proved more effective offensively than torpedo boats, and assumed the attack role. By the end of World War I, they were simply known as "destroyers." 
The destroyer during World War II continued in this role as an all-purpose ship ready to fight off attack from the air, on the surface, or from below the sea. It could be called upon to give fire support to troops, deliver mail and people to other ships, rescue pilots who had been forced down at sea, and to serve as the distant early warning eyes of the fleet in hostile waters.  Destroyers did not have the glamour of a battleship or an aircraft carrier, but without them the aircraft carrier and battleship would be helpless against enemy submarines. They were all-purpose ships whose support of general fleet operations was vital. No aircraft or battleship ever proceeded into enemy waters without an escort of destroyers.
USS Joseph P. Kennedy, Jr. represents American destroyers that fought against Japan in World War II for the following reasons:
Boulding, Christine. "National Register of Historic Places Inventory USS Joseph P. Kennedy, Jr." Boston, Massachusetts: Massachusetts Historical Commission,
Chesnau, Roger, ed., Conway's All the World's Fighting Ships 1922-1946. New York: Mayflower Books, 1980.
Harmon, Judd Scott. The USS Cassin Young (DD-793). Missoula, Montana: Histories Publishing Company, 1985.
No Author, USS Kidd Information Brochure, 1984.
Preston, Anthony. Destroyers. Englewood Cliffs, New Jersey: Prentice Hall, 1977.
Schofield, William G. Destroyer--60 Years. New York: Rand McNally & Company, 1962.
(click on the above photographs for a more detailed view)