Featuring 8"/55 caliber guns and designed to function as fleet flagships, the Portland class were intended to fix problems with armament and armor that had been a weakness of preceding U.S. cruisers.

On 30 July 1945, after transporting components for the nuclear weapons Little Boy and Fat Man from the United States, she was torpedoed by the Japanese submarine I-58.

The first "treaty cruisers" were the two of the Pensacola class ordered in 1926, which emphasized armament and speed at the expense of protection.

These ships were followed by the six vessels of the Northampton class ordered in 1927 with slightly better armor, and introduced the configuration of three triple turrets which would become standard on U.S. Navy heavy cruisers.

[citation needed] Ordered for the U.S. Navy in fiscal year 1930, the Portland class was originally designated as a light cruiser, and given the hull classification symbol CL, being re-designated a heavy cruiser with the symbol CA on 1 July 1931,[3] due to their armament, in accordance with the London Naval Treaty.

[4] The first three New Orleans-class cruisers, New Orleans, Astoria, and Minneapolis, were initially ordered as Portland-class vessels, but were reordered to the design of USS Tuscaloosa (CA-37).

[5] The ships featured two distinctive raked funnels, a tripod foremast, and a small tower and pole mast aft.

In 1943, light tripods were added forward of the second funnel on each ship, and a prominent Naval director was installed aft.

[3] The cruisers were armed with a main battery of nine Mark 9 8"/55 caliber guns arrayed in three triple mounts, a superfiring pair fore and one aft.

By 1945, the anti-aircraft defenses of both ships had repeatedly been upgraded, with each eventually receiving twenty four Bofors 40 mm guns.

[11] The New Orleans class was designed with these lessons in mind, intended to create a better balance between protection, armament and speed.

After the start of World War II, Portland took part in the Battle of Coral Sea, there rescuing 722 survivors from the sunk aircraft carrier Lexington.

[18] Indianapolis served as flagship of Scouting Force 1 during World War II, and saw action in a number of campaigns in the Pacific theater.

[19] In mid-1945, she sailed from the United States to Tinian Island carrying components of Little Boy and Fat Man, the two nuclear weapons which would later be used to bomb Hiroshima and Nagasaki.

Sailing for Leyte unescorted under Captain Charles B. McVay III, she was sunk by Japanese submarine I-58 on 30 July 1945, sinking in just 12 minutes.

[19][20] Following years of efforts by some survivors and others to clear his name, McVay was posthumously exonerated by the 106th United States Congress and President Bill Clinton on 30 October 2000.