Design and construction
on the slipway, 1925
the fourth US Navy ship named after the 1775
Battle of Lexington, the first battle of the
 She was originally authorized in 1916 as a
Lexington-class battlecruiser, but construction was delayed so that higher-priority
anti-submarine vessels and merchant ships, needed to ensure the safe passage of personnel and materiel to Europe during Germany's
U-boat campaign, could be built. After the war the ship was extensively redesigned, partially as a result of British experience.
 Given the
hull number of CC-1, Lexington was laid down on 8 January 1921 by
Fore River Shipbuilding Company of
Washington Naval Conference concluded, the ship's construction was suspended in February 1922,
 when she was 24.2 percent complete.
 She was re-designated and re-authorized as an aircraft carrier on 1 July 1922.
 Her displacement was reduced by a total of 4,000 long tons (4,100 t), achieved mainly by the elimination of her main armament of eight 16-inch (406 mm) guns in four twin turrets (including their heavy turret mounts, their armor, and other equipment).
 The main
armor belt was retained, but was reduced in height to save weight.
 The general line of the hull remained unaltered, as did the torpedo protection system, because they had already been built, and it would have been too expensive to alter them.
The ship had an
overall length of 888 feet (270.7 m), a beam of 106 feet (32.3 m), and a
draft of 30 feet 5 inches (9.3 m) at
deep load. Lexington had a
standard displacement of 36,000 long tons (36,578 t) and 43,056 long tons (43,747 t) at deep load. At that displacement, she had a
metacentric height of 7.31 feet (2.2 m).
Christened by Helen Rebecca Roosevelt, the wife of the
Assistant Secretary of the Navy,
Theodore Douglas Robinson, Lexington was launched on 3 October 1925. She was commissioned on 14 December 1927 with
Albert Marshall in command.
 By 1942, the ship had a crew of 100 officers and 1,840 enlisted men and an aviation group totaling 141 officers and 710 enlisted men.
Flight deck arrangements
The ship's flight deck was 866 feet 2 inches (264.01 m) long and had a maximum width of 105 feet 11 inches (32.28 m).
 When built, her
hangar "was the largest single enclosed space afloat on any ship"
 and had an area of 33,528 square feet (3,114.9 m2). It was 424 feet (129.2 m) long and 68 feet (20.7 m) wide. Its minimum height was 21 feet (6.4 m), and it was divided by a single
fire curtain just forward of the aft
aircraft elevator. Aircraft repair shops, 108 feet (32.9 m) long, were aft of the hangar, and below them was a storage space for disassembled aircraft, 128 feet (39.0 m) long. Lexington was fitted with two hydraulically powered elevators on her centerline. The forward elevator's dimensions were 30 by 60 feet (9.1 m × 18.3 m) and it had a capacity of 16,000 pounds (7,300 kg). The aft elevator had a capacity of only 6,000 pounds (2,700 kg) and measured 30 by 36 feet (9.1 m × 11.0 m).
Avgas was stored in eight compartments of the torpedo protection system, and their capacity has been quoted as either 132,264 US gallons (500,670 l; 110,133 imp gal) or 163,000 US gallons (620,000 l; 136,000 imp gal).
Lexington was initially fitted with electrically operated
arresting gear designed by
Carl Norden that used both fore-and-aft and transverse wires. The longitudinal wires were intended to prevent aircraft from being blown over the side of the ship while the transverse wires slowed them to a stop. This system was authorized to be replaced by the hydraulically operated
Mk 2 system, without longitudinal wires, on 11 August 1931. Four improved Mk 3 units were added in 1934, giving the ship a total of eight arresting wires and four
barriers intended to prevent aircraft from crashing into parked aircraft on the ship's bow. After the forward flight deck was widened in 1936, an additional eight wires were added there to allow aircraft to land over the bow if the landing area at the stern was damaged.
 The ship was built with a 155-foot (47.2 m),
flywheel-powered, F Mk II
aircraft catapult, also designed by Norden, on the starboard side of the bow.
 This catapult was strong enough to launch a 10,000-pound (4,500 kg) aircraft at a speed of 48
knots (89 km/h; 55 mph). It was intended to launch
seaplanes, but was rarely used; a 1931 report tallied only five launches of practice loads since the ship had been commissioned. It was removed during the ship's 1936 refit.
Lexington was designed to carry 78 aircraft, including 36
 but these numbers increased once the Navy adopted the practice of tying up spare aircraft in the unused spaces at the top of the hangar.
 In 1936, her air group consisted of 18
Grumman F2F-1 and 18
Boeing F4B-4 fighters, plus an additional nine F2Fs in reserve. Offensive punch was provided by 20
Vought SBU Corsair
dive bombers with 10 spare aircraft and 18
Great Lakes BG
torpedo bombers with nine spares. Miscellaneous aircraft included two
Grumman JF Duck
amphibians, plus one in reserve, and three active and one spare
Vought O2U Corsair observation aircraft. This amounted to 79 aircraft, plus 30 spares.
The Lexington-class carriers used turbo-electric propulsion; each of the four propeller shafts was driven by two 22,500-
shaft-horsepower (16,800 kW)
electric motors. They were powered by four
turbo generators rated at 35,200
hp). Steam for the generators was provided by sixteen
Yarrow boilers, each in its own individual compartment.
 Six 750-kilowatt (1,010 hp)
electric generators were installed in the upper levels of the two main turbine compartments to provide power to meet the ship's
hotel load (minimum electrical) requirements.
The ship was designed to reach 33.25 knots (61.58 km/h; 38.26 mph),
 but Lexington achieved 34.59 knots (64.06 km/h; 39.81 mph) from 202,973 shp (151,357 kW) during
sea trials in 1928.
 She carried a maximum of 6,688 long tons (6,795 t) of
fuel oil, but only 5,400 long tons (5,500 t) of that was usable, as the rest had to be retained as
ballast in the port fuel tanks to offset the weight of the
island and main guns.
 Designed for a range of 10,000
nautical miles (19,000 km; 12,000 mi) at a speed of 10 knots (19 km/h; 12 mph),
 the ship demonstrated a range of 9,910 nmi (18,350 km; 11,400 mi) at a speed of 10.7 knots (19.8 km/h; 12.3 mph) with 4,540 long tons (4,610 t) of oil.
firing her eight-inch guns, 1928
Bureau of Construction and Repair was not convinced when the class was being designed that aircraft could effectively substitute as armament for a warship, especially at night or in bad weather that would prevent air operations.
 Thus the carriers' design included a substantial gun battery of eight 55-
Mk 9 eight-inch guns in four twin
gun turrets. These turrets were mounted above the
flight deck on the starboard side, two before the
superstructure, and two behind the funnel, numbered I to IV from bow to stern.
 In theory the guns could fire to both sides, but it is probable that if they were fired to port (across the deck) the blast would have damaged the flight deck.
 They could be depressed to −5° and elevated to +41°.
The ship's heavy
antiaircraft (AA) armament consisted of twelve 25-caliber
Mk 10 five-inch guns which were mounted on single mounts, three each fitted on
sponsons on each side of the bow and stern.
 No light AA guns were initially mounted on Lexington, but two sextuple .30-caliber (7.62 mm)
machine gun mounts were installed in 1929.
 They were unsuccessful, and they were replaced by two .50-caliber (12.7 mm) machine guns by 1931, one each on the roof of the
superfiring eight-inch turrets. During a refit in 1935, platforms mounting four .50-caliber machine guns were installed on each corner of the ship, and an additional platform was installed that wrapped around the funnel. Six machine guns were mounted on each side of this last platform. In October 1940, four 50-caliber
Mk 10 three-inch AA guns were installed in the corner platforms; they replaced two of the .50-caliber machine guns which were remounted on the tops of the eight-inch gun turrets. Another three-inch gun was added on the roof of the deckhouse between the funnel and the island. These guns were just interim weapons until the quadruple
1.1-inch gun mount could be mounted, which was done in August 1941.
In March 1942, Lexington's eight-inch turrets were removed at Pearl Harbor and replaced by seven quadruple 1.1-inch gun mounts. In addition 22
Oerlikon 20 mm cannon were installed, six in a new platform at the base of the funnel, 12 in the positions formerly occupied by the ship's boats in the sides of the hull, two at the stern, and a pair on the aft
control top. When the ship was sunk in May 1942, her armament consisted of 12 five-inch, 12 quadruple 1.1-inch, 22 Oerlikon cannon, and at least two dozen .50-caliber machine guns.
Fire control and electronics
Each eight-inch turret had a Mk 30
rangefinder at the rear of the turret for local control, but they were normally controlled by two Mk 18
fire-control directors, one each on the fore and aft spotting tops.
 A 20-foot (6.1 m) rangefinder was fitted on top of the
pilothouse to provide range information for the directors.
 Each group of three five-inch guns was controlled by a Mk 19 director, two of which were mounted on each side of the spotting tops.
 Lexington received a
radar in June 1941 during a brief refit in Pearl Harbor. The
antenna was mounted on the forward lip of the funnel with its control room directly below the aerial, replacing the secondary
conning station formerly mounted there.
belt of the Lexington-class ships tapered 7–5 inches (178–127 mm) in thickness from top to bottom and angled 11° outwards at the top. It covered the middle 530 feet (161.5 m) of the ships. Forward, the belt ended in a
bulkhead that also tapered from seven to five inches in thickness. Aft, it terminated at a seven-inch bulkhead. This belt had a height of 9 feet 4 inches (2.8 m). The third deck over the ships' machinery and
magazine was armored with two layers of
special treatment steel (STS) totaling 2 inches (51 mm) in thickness. The steering gear, however, was protected by two layers of STS that totaled 3 inches (76 mm) on the flat and 4.5 inches (114 mm) on the slope.
The gun turrets were protected only against splinters with 0.75 inches (19 mm) of armor. The conning tower was 2–2.25 inches (51–57 mm) of STS, and it had a communications tube with two-inch sides running from the conning tower down to the lower conning position on the third deck. The
torpedo defense system of the Lexington-class ships consisted of three to six medium steel
protective bulkheads that ranged from 0.375 to 0.75 inches (10 to 19 mm) in thickness. The spaces between them could be used as fuel tanks or left empty to absorb the detonation of a torpedo's