* Antiaircraft armament as during the Battle of Midway (June 1942).

The six Northampton class heavy cruisers were built to add more firepower to the U.S. Navy's battle fleet which couldn't build any additional battleships due to the 1922 Washington Naval Treaty. The ships were based on the Pensacola class heavy cruisers, though the Northamptons mounted only nine 8 in (203 mm) guns in three triple turrets (instead of ten in two triple and two twin turrets on Pensacolas), the layout followed in all subsequent U.S. heavy cruisers. These cruisers were also the first U.S. ships to adopt a hangar for aircraft and bunks instead of hammocks. Although armor was increased the North­amptons turned out to be lighter than the Pensacolas, and nearly 1,000 tons below the treaty limitations. The first three ships were equipped as flagships with an additional complement of around 750.

The cruisers were initially armed also with four 5 in (127 mm) double purpose guns, eight .50 in (12.7 mm) AA machine guns, and six 21 in (533 mm) torpedo tubes. But before World War II began, the torpedo tubes were removed due to wargaming results from the Naval War College which indicated that the torpedoes were unlikely to be fired from a cruiser, and more a liability than an asset. At the same time, the anti-aircraft armament was increased with four additional 5 in (127 mm) guns and four of the new four-barrel 1.1 in (28 mm) auto­cannons.

One Northampton class heavy cruiser (CA-26 Northampton) took part in the Battle of Midway as a flagship of Task Force 16 Cruiser Group (Task Group 16.2).