Construction
She and her sister ship Saratoga were originally authorized in 1916 as battle cruisers of 35,300 tons with seven funnels and boilers disposed on two deck levels. After the war, and as a result of the lessons thereof, plans were to a large extent re-cast in 1919. Designated CC-1 and CC-3, they were laid down as smaller battle cruisers on 8 January 1921 by Fore River Shipbuilding Company, Quincy, Massachusetts.

Following the Washington Naval Conference, they were both redesignated and re-authorized to be completed as aircraft carriers on 1 July 1922. As such, they were reduced in displacement by 8,500 tons, achieved mainly by the elimination of eight 16-inch (406 mm) guns in four twin turrets (including mounts, armor, and so on). The main belt armor was retained, and the deck armor was heavily reinforced. The general lines of the hull remained unaltered, and the special system of underwater protection was adhered to. The flight deck was 880 feet (244m) long and 85 to 90 feet (25.9-27.4m) wide, mounted 60 feet (18.3m) above the waterline. The mean draught was 24 feet 1.5 inches (7.4m). The ships had a complement of 169 officers and 1730 men, including flying personnel. They carried eight 8 inch (203 mm)/55 caliber guns, twelve 5-inch (127 mm)/25 caliber anti-aircraft guns, and four 6-pounder (2.24-inch, 57 mm) saluting guns. These two ships were the last two built with a transverse catapult as part of the original design. The catapult had a travel of 155 feet (47 m), and was strong enough to launch the heaviest naval aircraft then in existence within 60 feet (18.3m). As built, these two ships had cranes for launching and retrieving seaplanes and flying boats, a capability removed during the war and replaced by additional anti-aircraft guns. The ships were designed to carry a maximum of 120 aircraft of various types, including fighters, scouts, and bombers. Each ship cost a total of $45,000,000 with aircraft.

Lexington was launched 3 October 1925, sponsored by Mrs. Theodore Douglas Robinson (wife of the Assistant Secretary of the Navy), and commissioned 14 December 1927, Captain Albert W. Marshall in command.

Lexington and Saratoga had turboelectric drive with 16 Yarrow boilers powering four General Electric steam turbines spinning generators that powered the four slower speed main drive motors. Lexington's engines provided electricity to Tacoma, Washington for thirty days during a power shortage in the winter of 1929/1930.
After fitting out and shakedown, Lexington joined the Battle Fleet at San Pedro, California, 7 April 1928. Based there, she operated on the west coast with Aircraft Squadrons, Battle Fleet, in flight training, tactical exercises, and battle problems. Each year she participated in fleet maneuvers in Hawaii, in the Caribbean, off the Panama Canal Zone, and in the eastern Pacific. On trials, Lexington achieved an average speed of 30.7 knots, and maintained a speed of 34.5 knots for one hour