The last two ships of the class, and , were slightly modified versions of the design with new higher pressure boilers and a unit system of machinery that alternated boiler and engine rooms to prevent a ship from being immobilized by a single unlucky hit; this system would be used in all subsequent US cruisers. Additionally, AA armament was improved. They were the first US cruisers to be armed with twin 5-inch (127 mm)/38-caliber guns. They could be distinguished visually from the other Brooklyns by the placement of the after deckhouse, immediately abaft the second funnel, and by the twin 5-inch mounts.
