Curtiss designed the Model CW-20 as a passenger plane capable of carrying 36 passengers in the mid-1930s. The prototype had a twin tail (similar to the Beech C-45), but after initial flight testing in the spring of 1940, the plane was extensively modified including the replacement of the twin tail with a conventional design.

The Air Corps was interested in the improved design and ordered 46 planes designated as the C-46 in July 1940. The Air Corps bought the prototype CW-20 a year later in June 1941 and designated it C-55. The first C-46 was delivered to the Air Corps in the summer of 1942.

A proposed postwar commercial version was the CW-20E, but it failed to attract customer interest and thus all Commandos to enter civilian service were ex-military aircraft. Most were purchased by American operators for freight work. One postwar version though was the Riddles Airlines C46R which had more powerful engines and better performance. Thirty or so were converted.