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

Even before the commissioning of six Northampton class cruisers, U.S. Navy ordered five more heavy cruisers of the almost same design. The ships were laid down in 1930-1931, but the follow-on class of cruisers (CA-37 Tuscaloosa) exhibited such superior characteristics, that an attempt was made to reorder all five ships under construction to its specifications. However, two cruisers the CA-33 Portland and the CA-35 Indianapolis had been awarded to private builders and contract changes would be far too expensive, thus the Portland class was relegated to just two cruisers. The remaining three ships were all at Navy yards and could be modified without great expense, they became the part of the follow-on New Orleans class.

The ships were built to a modified design with a modified superstructure and minor improvements. Both ships were fitted out as flagships, providing enough room for an admiral and his staff. The cruisers, like their Northampton class predecessors, used three triple-turret layout for their 8 in (203 mm) guns, but originally mounted twice as many 5 in (127 mm) dual-purpose guns (8 vs 4), and were somewhat heavier. The Portland class ships also were the first U.S. cruisers built without torpedo tubes 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.

One Portland class heavy cruiser (CA-33 Portland) took part in the Battle of Midway as a part of Task Force 17 Cruiser Group (Task Group 17.2).