[C] The idea for a large cruiser class originated in the early 1930s when the USN sought to counter the Deutschland-class "pocket battleships" being launched by Germany.

Of the six planned, Alaska and Guam were the only two to be commissioned; a third, Hawaii, was close to completion at the war's end and had its construction suspended on 16 April 1947, while the remaining three were cancelled.

Alaska and Guam served with the USN for the last year of World War II as bombardment ships and fast carrier escorts.

Heavy cruiser development formalized between World War I and World War II due to the terms of the Washington Naval Treaty and successor treaties and conferences, where the United States, Britain, Japan, France, and Italy agreed to limit heavy cruisers to 10,000 tons displacement with 8-inch main armament.

[13][4][10][14][E] The navy responded in 1938 when the General Board asked the Bureau of Construction and Repair to conduct a "comprehensive study of all types of naval vessels for consideration for a new and expanded building program".

[15] The US president at the time, Franklin Delano Roosevelt, may have taken a lead role in the development of the class with his desire to have a counter to raiding abilities of Japanese cruisers and German pocket battleships.

[20] The General Board, in an attempt to keep the displacement under 25,000 tons, allowed the designs to offer only limited underwater protection such that they were vulnerable, by comparison with a battleship, to torpedoes and to shells that fell short of the ship.

In addition, the large cruiser design did not include the extensive underwater protections found in normal carriers due to the armor weight devoted to counter shell fire.

[13][15] The last three, Philippines, Puerto Rico, and Samoa, were delayed since all available materials and slipways were allocated to higher priority ships, such as aircraft carriers, destroyers, and submarines.

[27][28][29] Alaska and Guam served with the U.S. Navy during the last year of World War II, forming Cruiser Division 16 commanded by Rear Admiral Francis S. Low, USN.

Guam, joined by Alaska, four light cruisers, and nine destroyers, led the task force into the East China and Yellow Seas to conduct raids upon shipping; however, they encountered only Chinese junks.

These naval demonstrations preceded Operation Chromite, the amphibious landing of U.S. Army ground forces at Incheon, Korea, on 10 September 1950.

[20] In 1958, the Bureau of Ships prepared two feasibility studies to explore whether Alaska and Guam could be suitably converted into guided-missile cruisers.

However, the designation was changed to CB to reflect their new status, "large cruiser", and the practice of referring to them as battlecruisers was officially discouraged.

[12] Author Richard Worth remarked that when they were finally completed, launched, and commissioned, they had the "size of a battleship but the capabilities of a cruiser".

The Alaska class was similarly expensive to build and maintain as contemporary battleships, yet far less capable due to armor deficiencies, while able to put up an anti-aircraft defense comparable only to the much cheaper Baltimore cruisers.

[39] The official navy magazine All Hands said "The Guam and her sister ship Alaska are the first American battle cruisers ever to be completed as such.

"[40] Author Chris Knupp noted that while "other nations fulfilled the battlecruiser role by designing vessels like battleships, but stripped of armor and other features to gain speed", the United States "fulfilled the battlecruiser role by creating a larger, more powerful heavy cruiser...[whose] design already offered less armor and higher speed, but by enlarging the ship they gained the heavier firepower".

[44] Designed in 1939, it weighed 121,856 pounds (55,273 kg) including the breech, and could sustain an average rate of fire of 2.4–3 rounds a minute.

[17] The secondary battery of the Alaska class was composed of twelve dual-purpose (anti-air and anti-ship) 5"/38 caliber guns in twin mounts, with four offset on each side of the superstructure (two on each beam) and two centerline turrets fore and aft.

The 5"/38 was originally intended for use on only destroyers built in the 1930s, but by 1934 and into World War II it was being installed on almost all of the U.S.'s major warships, including aircraft carriers, battleships, and heavy and light cruisers.