In describing the Iowa class of battleships, several points come to mind immediately. First, the most astonishing fact is that after fifty-five years of service with the U.S. Fleet, the United States still is unwilling to part with the capabilities of these by now unique vessels.
Second, they were in all likelihood the most capable of their kind ever to bury their bows in to the waves of the ocean.
And third, the class proved a change from the design philosophies previously held up by U.S. constructors.

For the follow-on class to South Dakota, the U.S. Navy considered a usual assembly of slow and fast battleship designs, some sporting more armament or heavier protection, and some favoring better speed. In March 1938, after evaluating the possibilities of constructing a fast battleship within the limits still imposed by the – now escalated --  Washington Treaty, the General Board picked a scheme which proposed a 33-knot South Dakota class vessel at roughly 40.000 tons. Five thousand tons, which was the margin of error or addition that the U.S. planners left their design, seemed enough room to build a fine warship, alas with passing time it became obvious that even the full use of the additional 10.000 tons compared to South Dakota would yield little more than six knots of speed.
With that in mind, the General Board chose to adopt a gun which dated to 1922, a 16”/L50 gun originally scheduled for vessels like the Constellation class battlecruisers.
While the designers re-shaped the hull to accomodate the new gun, troubles arose because the 45.000 tons limit had been broken with the L/50 gun; a lighter turret was needed. The idea was soon completed: an indeed, on paper, it worked out fine. The General Board received a balanced 45.000 tons design with 9 16” guns and 33-knot speed.
However, in the steps of committing the design to a contractable proposal, BuOrd had designed a turret that would not fit the ship, while the lighter turret which would have worked was found to have not passed the initial phases of design.
An immediate solution was needed to avoid building a 45.000 ship with nothing gained but six knots of speed. With no turret to match gun and ship, and no ship to match turret and gun, BuOrd hastily designed a lightweight 16”L/50 gun which would fit a turret that would fit the ship.
The process of refining the design continued; New York Naval Yard subdivided the machinery for better protection and added more transverse bulkheads. In September 1939, with the outbreak of war in Europe, the last restrictions of the Washington Treaty were suspended by warfighting nations Great Britain and France. So the additional weight of these actions was gladly accepted.
Sharing all the armor system of the South Dakota class, the Iowas also possessed the rather inadequate underwater protection With some late additions came a bit more armor and bulkheads, but only for the two later vessels; Iowa and New Jersey were too valuable to be delayed by minor improvements.
Iowa and New Jersey were ordered in FY39,  Missouri and Wisconsin in FY41. Accompanying the latter two were the final pair, Illinois and Kentucky, destined to remain incomplete.
As noted earlier, one of the most amazing features of this class is its longevity. The first vessel was commisioned in 1943; the entire class arrived early enough to see service in the war, forming the most potent anti-aircraft platform in the fleet. With the post-war demobilization, the fleet lost three of the ships to mothballs, but when the Korean War began in 1950, the Navy quickly remobilized all ships. Their valuable service on the gunline more than validated the concept of heavy guns, and following the end of the war, the ships again were put into mothballs.
During the Vietnam War, the fleet reactivated New Jersey and utilized her in bombarding enemy positions along the shore. Although this time, her sisterships were not put back into service, the value of New Jersey's support prevented their scrapping yet again.
Finally, in 1982, the threat from the Soviet Union's new nuclear-powered Kirov large cruisers of 28.000 tons gave the impetus to reactivate the Iowa class and modernize it. Under the Reagen administration, all four ships received Tomahawk cruise missiles, modern radars and jammers, and rapid-fire point-defense gun systems. For ten years, the reactivated battleships supported operations along the shore of the Mediterranean and Persian Gulf, shelling Syrian and Iraqi positions and providing some long-range firepower with their missiles. With the post-cold war arms reduction, the battleships were doomed to finally leave the fleet; Missouri became a floating memorial next to Arizona at Pearl Harbor; New Jersey is bound to be a memorial in her state. But Congress refused to take the battleship out of the fleet for good: it passed legislation demanding that under full mobilization, two battleships would yet be available. Maybe the story of the battleship has not yet ended.
 
Ships in class:
BB-61 Iowa
BB-62 New Jersey
BB-63 Missouri
BB-64 Wisconsin
BB-65 Illinois (not completed)
BB-66 Kentucky (not completed)