In October 1941, the American army ordered the development of a recovery vehicle and a trailer for the transport of medium-weight tanks. The order also stated that the vehicle could easily get through difficult terrain and an armored cabin. The trailer was developed by the American manufacturer Fruehauf. The M26 tractor was developed by the Knuckey Truck Company from California. This company was specialized in heavy terrain vehicles. Based on the design, the army ordered a first vehicle in mid-1942 which was delivered in September 1942. The test showed that the combination of tractor and trailer was successful and the army wanted to order the combination. However, the production capacity of Knuckey was not large enough and the Pacific Car & Foundry of Seattle, Washington, received the construction order. Production of the M26 started in May 1943 and a total of 753 units were built . In 1944 an unarmored version, the M26A1, was developed, of which another 619 were made. After the war, the latter was modified and given the designation M26A1. The most important improvement was a 24-volt electrical system.