The Grumman Aircraft Engineering Corporation of Bethpage, New York, was one of the most important builders of military aircraft in the 20th century. From the company's beginning in 1930, through the end of World War II, Grumman designed and built several U .S. Navy aircraft that established the firm's reputation for outstanding aeronautical engineering. Although the Long Island company also contributed significantly to commercial aviation, it was Grumman's navy planes, particularly its series of World War II combat aircraft, that assured the company's success. As Rear Admiral John S. McCain would note in 1942: "The name Grumman on a plane…[had] the same meaning to the Navy that 'sterling' [had] on silver." To the Navy, Grumman aircraft were the highest quality planes that money could buy.

Six men started the Grumman Corporation on January 2, 1930, in a small garage in Baldwin, New York. Leroy Grumman (a former naval aviator) and William Schwendler headed the operation. They were both former engineers at the Loening Company, another successful builder of navy planes during the 1910s and 1920s, and the two understood the challenges of naval aircraft design. Albert Loening had sold his business in 1928, and Grumman believed it stood a good chance of filling the void left behind.

Grumman's first major technological improvement occurred between 1931 and 1933 when Grumman and Schwendler convinced the Navy to let them develop a new fighter and a new scout plane. These aircraft had an innovative type of retractable landing gear that allowed the plane to touch down on an aircraft carrier, and also land and float on water—something that had not been done before. They placed this lighter retractable gear design (which contained Grumman's specially patented aluminum) on their new fighter, the FF-1 "Fert'l Myrt'l," a two-seat, bi-wing that primarily launched from airfields and carriers but which could also land on water and stay afloat if necessary. The JF-1 "Duck" was Grumman's scout plane version of the FF-1, with a special flotation device attached. Both planes, and the subsequent F3F, a single seat version of the FF-1, pleased navy officials immensely and became key naval aircraft during the 1930s.

Grumman had a close relationship with the Navy, but by the mid 1930s, company officials were worried about the firm's sole reliance on military business and decided to also design planes for the commercial market. The company's first ventures into the non-military realm occurred in 1936 when it developed the G-21 "Goose" and the G-22 "Gulfhawk." The Goose filled the needs of a small group of New York businessmen who wanted a water taxi service for commuting more efficiently between their Wall Street waterfront offices and their remote Long Island estates. It was a two-engine, mono-wing seaplane that held eight passengers and two crew members. By World War II, the Goose had proved itself versatile enough that both the Navy and Army Air Corps were using modified versions.

The Gulfhawk was made-to-order for the famous stunt pilot and one time air speed record holder Major Al Williams. A former naval aviator, Williams had long admired Grumman engineering, and when he needed a new acrobatic plane, he had Grumman build it. The Gulfhawk was a highly maneuverable single-engine, biplane with a maximum speed of 290 miles per hour (467 kilometers per hour), and in Williams's hands, it performed brilliantly. During the late 1930s, it was a major attraction at air shows worldwide.

Unlike several aircraft companies whose businesses suffered during the Great Depression, Grumman had to increase its factory space and workforce considerably during the 1930s because of its military business. In 1937, the company moved to Bethpage, Long Island, and built a new factory. By the fall of 1941, Grumman had grown to approximately 6,500 workers. But the expansion did not stop there. To produce all of the planes the Navy needed during World War II, Grumman's workforce grew at a rate of 1,000 workers a month until it peaked in September 1943 at about 25,500 employees. Its floor space also increased by a factor of 25 to approximately 2.65 million square feet (246,193 square meters). Grumman plants operated 24 hours a day and produced more military planes than any other company during the war. In March 1945 alone, Grumman set the war record for the most deliveries by a single factory when it cranked out 664 aircraft.

Grumman's first major warplane was the innovative F4F Wildcat, a single-seat, single-engine, carrier-based strike fighter equipped with a unique Grumman invention called "sto-wings, which allowed a plane's wings to fold in half for easy storage on cramped aircraft carriers. It had six machine guns and two 100-pound (45-kilogram) bombs and was also Grumman's first mono-wing fighter. Unfortunately, the Japanese Zero airplane was faster and often outperformed it. Nevertheless, many U.S. pilots still held their own in dogfights because of the Wildcat's excellent diving and rolling ability. In fact, New York Times correspondent Foster Hailey believed the Wildcat "did more than any single instrument of war to save the day for the United States in the Pacific."

Grumman's TBF "Avenger" also contributed significantly to the Allied victory over Japan and Germany. The Avenger was a single-engine, mono-wing, torpedo bomber that held a pilot, a turret gunner, and a radioman/bombardier. When fully loaded with bombs and torpedoes, the TBF was twice the weight of the Wildcat. With a machine gun turret mounted behind the pilot, the Avenger was a formidable combat plane and performed extremely well on low-altitude attacks and dive-bombing runs. The Navy used the Avenger effectively against enemy submarines, particularly in tandem with Wildcats. Grumman delivered the first TBFs to the Navy in January 1942.

Grumman built one of the classic combat planes of World War II, the F6F "Hellcat." Essentially a more sophisticated version of the F4F Wildcat, Grumman engineers specifically designed it to defeat the Japanese Zero. It could fly about 60 miles per hour (97 kilometers per hour) faster than the Wildcat, about 300 miles (403 kilometers) farther without refueling, and carry more armament. Like the F4F, the Hellcat was a single-seat, single-engine, strike fighter with sto-wings. The first Hellcats saw action in the Pacific in September 1943 and quickly gained a reputation for outstanding performance and craftsmanship. Many sustained extensive combat damage and still returned their pilots safely home. Airmen often referred to the Grumman company as the "Iron Works" because its planes seemed indestructible. Grumman produced 12,272 Hellcats from June 1942 to November 1945, the largest number of fighters ever made in a single aircraft factory. Naval aviators racked up an impressive record with the Hellcats; of the 6,477 aerial victories they claimed during the war, 4,947 went to F6F pilots. In short, the Hellcat was a terrific and highly reliable plane and U.S. aviators loved it. One unidentified pilot simply noted about his beloved F6F: "If my Hellcat could cook, I'd marry it."

From its humble beginnings in 1930, to its impressive production records and designs during the Second World War, Grumman established itself as one of the most important military aircraft builders of the century. But with the end of the war, the company would go through some substantial changes. Although Grumman would continue to secure navy business after the war, the government's needs would change enough to force the company to reshape itself. By the late 1950s, Grumman would suddenly be building spacecraft and designing more planes for the commercial market.