The Portland class was basically a Northampton class, lengthened by 3 meters and displacing, empty, exactly 10.000 tons. The additional weight was well used for more armor around the ship, further increasing the protection, which was not yet proper.

    Originally, there had been plans for five ships of this class, but since armor armor protection was not yet deemed adequate, the class was cut short at two vessels. Armament was the same as in the Northampton class: three triple turrets housing 203mm guns. These vessels never had torpedo tubes, and always held eight 127mm L/25 flak guns.  
Portland participated in the Battle of the Coral Sea and Midway, later at Guadalcanal and the Battle of Santa Cruz. At the First Battle of Guadalcanal, Portland under Captian DuBose suffered a dangerously critical torpedo hit, but survived the engagement. After temporary service in the Aleutians after her repairs, she continued to serve in the Central Pacific in all major campaigns and was finally decommisioned in mid-1946.

    Indianapolis was not so much in action, serving in the South Pacific for a short while in 1942, before missing Coral Sea and Midway due to a yardtime. Then she bombarded Attu and Kiska in the Aleutians, and served as flagship of Admiral Raymond Spruance as COM5THFLT. Served with the fleet thereafter in all major campaigns up to Okinawa, from where she waqs recalled to transport the A-bombs to Tinian. Then, she departed from Guam to Okinawa and was sunk on the way by two torpedoes from I-58, which was helped by inproper sealing of bulkheads in the ship. Lost 883 men with only 316 men rescued, marking the last major warship loss in the US Navy.