Marquardt Corporation was one of the few aeronautical engineering firms that was dedicated almost solely to the development of the ramjet engine. Marquardt designs were developed through the 1940s into the 1960s, but the ramjet never became a major design and the company turned to other fields in the 1970s. They suffered a particularly bad financial crisis with the ending of the Cold War, and went bankrupt in the 1990s.
Roy Marquardt was an aeronautical engineering graduate from Caltech who had worked at Northrop during World War II on the YB-35 flying-wing bomber project. While working on problems cooling the engines, which were buried in the wings, he found that the heat generated by the engines produced useful thrust. This started his interest in the ramjet principle, and in November 1944 he started Marquardt Aircraft in Venice, California to develop and sell ramjet engines. In the late 1940s the company relocated to Van Nuys, California, adjacent to the Van Nuys Airport.
Marquardt's first products were wind tunnels, but by the end of their first year they had delivered an experimental 20 inch (0.51 m) ramjet to the United States Navy for testing. The United States Army Air Forces purchased two of the same design early in 1946, and fitted them to the wingtips of a P-51 Mustang fighter for in-flight testing. By this time the Navy had fitted theirs to a F7F Tigercat and started flight tests in late 1946. Later Navy tests fitted the same engine to a XP-83 and F-82 Twin Mustang.