As such, the 16" gun Colorado-class ships were the last and most powerful battleships built by the U.S. Navy until the North Carolina class entered service on the eve of World War II.

The Colorados were the final group of the Standard-type battleships, designed to have similar speed and handling to simplify maneuvers with the line of battle.

This success, along with the unofficial news in several naval publications of 15- and 16-inch weapons being adopted by the United Kingdom, Italy, Germany and Japan, led the Board to consider cancelling the construction of the Pennsylvania class in favor of an up-gunned design.

Likewise, the Tennessees were the results of modifications to the New Mexico class, which had been the most modern U.S. Navy capital ships to see service in World War I and had attracted the attention of British constructors both serving with and outside C&R.

The U.S. Navy had done this by a process almost akin to the assembly line, sticking to one basic design per class with a maximum amount of standardization and rationalization.

Since the Naval Act of 1916 meant the imminent construction of 16 battleships and six battlecruisers, it was necessary to streamline production to save time and labor.

The problem was that tests in caissons—experiments that would eventually prove that a series of compartments divided between being filled with liquid and being left empty would be a very effective defense against torpedoes—were not yet complete.

Altogether, the ships' power plant was rated at 28,900 electrical horsepower (EHP) to provide a flank speed of 21 knots (39 km/h; 24 mph).

With a maximum bunker capacity of 4570 tons, the Colorados' range without refueling at sea was 10,000 nautical miles (19,000 km; 12,000 mi).

[10] The Colorado class was armed with eight 16-inch (406 mm)/45 caliber Mark 1 guns, which fired a 2,110-pound (960 kg) armor-piercing (AP) shell at a muzzle velocity of 2,600 feet per second (792 m/s) and a rate of about 1.5 rounds per minute to a range of 34,300 yards (31,400 m) at a maximum turret elevation of 30 degrees.

In addition, the eight boilers were moved from their location in previous designs and placed in separate spaces to port and starboard of the turboelectric power plant.

Also, the design called for the use of external, rather than internal, belt armor so that a "break in the continuity of the side structure" would not exist, which would minimize drag in the water and any corresponding waste of power.

Plans for modernization of the Tennessee and Colorado classes were made in October 1931, in part to take advantage of loopholes in the Washington Naval Treaty.

Also, the deck armor was to be bolstered with 80 lb (36 kg)-special treatment steel (STS)—which would add 1,319 long tons (1,340 t; 1,477 short tons) to the displacement of the ships—the armor on the tops of the main turrets was to be made thicker, fire controls were to be improved with the latest technology, and new shells for the main guns were to be designed.

Two (later four) quad 1.1-inch guns were to be added, and all of the machinery in place would be removed in favor of newer equipment so that the ships would not lose any speed with the great increase in weight.

Anti-torpedo bulges were also to be installed to improve buoyancy but not to increase the ships' beams any greater than 106 feet (32 m) so they could still use the Panama Canal when transferring from the Atlantic to the Pacific and vice verse.

An ultimate secondary battery of sixteen 5 in/38 in dual mounts, sixteen Bofors 40 mm in quadruple mounts and eight single Oerlikon 20 mm guns was called for by the board in 1941, although they were not certain the ships could handle the added weight and it would take a large amount of time in dry dock for these modifications to take place.

The King Board suggested that the deck armor be bolstered and 5 in/38 dual-purpose guns be added, but the Chief of Naval Operations decreed that any major changes such as these had to wait due to the wars raging around the world at the time.

The addition of bulges, however, was approved for the "Big Five", with each ship spending three months in dry dock at the Puget Sound Naval Shipyard.

Maryland would be first (17 February 1941 to 20 May), followed by West Virginia (10 May to 8 August), Colorado (28 July to 28 October), Tennessee (19 January 1942 to 21 April) and California (16 March to 16 June).

[30] Only two of the ships had bulges added to them through this program, Maryland (completed 1 August 1941) and Colorado (26 February 1942); the attack on Pearl Harbor interrupted the refits intended for West Virginia and the two Tennessees.

The surprise strike did not touch Colorado, which was at Puget Sound, and did not hurt Maryland very badly; however, West Virginia was severely damaged and needed a major refit at minimum.

[33] Colorado and Maryland were greatly needed in the war zone, and as such did not undergo a major refit until 1944, although minor additions and removals, mainly to the anti-aircraft weaponry, were made in-between.

While undergoing repair, eight twin 5 in/38 were added, but nothing else; her conning tower was removed and replaced by a 50 lb (23 kg) special-treated steel structure to balance the additional weight of the 5 in guns.

During her career, Colorado was involved in various ceremonies and fleet exercises, and assisted residents of Long Beach, California following the 1933 earthquake.

During her career she made a goodwill voyage to Australia and New Zealand in 1925, and transported President-elect Herbert Hoover on the Pacific leg of his tour of Latin America in 1928.

She was launched on 1 September 1921, but on 8 February 1922, two days after the signing of the Washington Naval Treaty, all construction work ceased on the 75.9% completed dreadnought.

On the first day of testing, the ship was hit by two 400-pound (180 kg) torpedoes and three 1 short ton (0.91 t) near-miss bombs with minor damage and a list of three degrees.

Despite a grounding incident early in her career West Virginia received high acclaim for gunnery and armor protection, and was involved in exercises to test the defenses of the Hawaiian Islands in the 1930s.

In February 1945 West Virginia participated in the Battle of Iwo Jima, initially by preinvasion bombardment, and later by callfire support for the ground forces on the island.