5"/51 caliber guns initially served as the secondary battery of United States Navy battleships built from 1907 through the 1920s, also serving on other vessels. United States naval gun terminology indicates the gun fired a projectile 5-inch (127 mm) in diameter, and the barrel was 51 calibers long.

The Florida-class battleships of the United States Navy comprised two ships: Florida and Utah. Launched in 1910 and 1909 respectively and commissioned in 1911, they were slightly larger than the preceding Delaware class design but were otherwise very similar. This was the first US battleship class in which all ships received steam turbine engines. In the previous Delaware-class, North Dakota received steam turbine propulsion as an experiment while Delaware retained triple-expansion engines.