The first U.S. 356mm guns were mounted in the New York, Nevada and Pennsylvania classes, in response to a general increase in gun caliber all over the globe. They were of 45 caliber lengths, but they suffered from constructional problems.

    The new L/50 version cured these problems. It was designed out of political necessity, so to speak. 
In 1910, the proposal to build a 406mm L/45 gun was looked upon with mixed feelings among the government, since an increase in gun caliber would certainly also mean an increase in battleship size and cost. Its was due to this that BuOrd, in parallel with the 406mm gun, developed a 356mm L/50 gun in case a 406mm battleship would not be authorized. As it happened, it wasn't, and thanks to that, the L/50 was employed in the Mississippi and Tennessee classes. Only the Marylands, authorized at the height of WWI, took the step to the 406mm gun -- without much increase in tonnage or cost.

   The initial gun had problems with dispersion, but these were worked out. In the end, it was a significant improvement over the earlier L/45.