The company was founded from the firms of James Smith McDonnell and Donald Wills Douglas. Both were graduates of MIT and had worked for the aircraft manufacturer Glenn L. Martin Company. Douglas had been chief engineer at Glenn L. Martin, he left and established Davis-Douglas Company in early 1920 in Los Angeles, he bought out his backer and renamed the firm the Douglas Aircraft Company in 1921.
McDonnel founded J.S. McDonnell & Associates in Milwaukee, Wisconsin in 1928. His idea was to produce a personal aircraft for family use. The economic depression from 1929 ruined his ideas and the company collapsed and he went to work for Glenn L. Martin. He left in 1938 to try again with his own firm, McDonnell Aircraft Corporation, this time based near St. Louis, Missouri.
The war was a major earner for Douglas as well, the company produced almost 30,000 aircraft from 1942 to 1945 and the workforce swelled to 160,000. The company produced a number of aircraft including the C-47 (based on the DC-3), the DB-7 (known as the A-20, Havoc or Boston), the Dauntless and the A-26 Invader. Both companies suffered at the end of hostilities, facing an end of government orders and a surplus of aircraft both heavily cut their workforces, Douglas sacking almost 100,000 people. As part of their wartime work Douglas had established a USAAF think-tank, a group that would later become the RAND Corporation
Douglas continued to develop new aircraft, including the successful four-engined DC-6 (1946) and their last prop-driven commercial aircraft the DC-7 (1953). The company had moved into jet propulsion, producing their first for the military - the conventional F3D Skyknight in 1948 and then the more 'jet age' F4D Skyray in 1951. Douglas also made commercial jets, producing the DC-8 in 1958 to compete with the new Boeing 707. McDonnell was also developing jets, but being smaller they were prepared to be more radical, building on their successful FH-1 Phantom to become a major supplier to the Navy with the Banshee, Demon, and the Voodoo. The advent of the Korean War helped push McDonnell into a major military fighter supply role, especially with the noted F-4 Phantom II (1958).
Both companies were eager to enter the new missile business, Douglas moving from producing air-to-air rockets and missiles to entire missile systems under the 1956 Nike program and becoming the main contractor of the Skybolt ALBM program and the Thor ballistic missile program. McDonnell made a number of missiles, including the unusual ADM-20 Quail, as well as experimenting with hypersonic flight, research that enabled them to gain a substantial share of the NASA projects Mercury and Gemini. Douglas also gained contracts from NASA, notably for part of the enormous Saturn V rocket.
Both companies were now major employers, but both were having problems, Douglas was strained by the cost of the DC-8 and DC-9, and began to sound each other out about a merger. Inquiries began in 1963, Douglas offered bid invitations from December 1966 and accepted that of McDonnell. The two firms were officially merged on April 28, 1967 as the McDonnell Douglas Corporation.
The new corporation continued its profitable association with the military, producing the F-15 Eagle (1974) and the F/A-18 Hornet (1975) as well as the Harpoon and Tomahawk missiles. The oil crisis of the 1970s was a serious shock to the commercial aviation industry and McDonnell Douglas was forced to contract heavily and also began to diversify to reduce the impact of potential future downturns. In 1984 the corporation acquired Hughes Helicopters.
In 1997 following the acquisition of Rockwell International by Boeing there was an enormous aerospace-defence merger between Boeing and McDonnell Douglas to create The Boeing Company.