Thermo King Model C

In 1939, Frederick McKinley Jones patented the world’s first successful refrigerated transportation system. At the time, he was working for the Minneapolis-based company U.S. Thermo Control. Two years later, he released an improved version, the Model C, which revolutionized the agriculture and military industries.

Frederick McKinley Jones patented more than sixty inventions over his sixty-seven-year lifetime, making him one of the most prolific African American inventors ever. The Thermo King Model C stands as his most prominent achievement.

While living in Hallock in the 1920s, Jones built a transmitter for the town’s radio station. Joe Numero, an entrepreneur from Minneapolis, noticed the station’s excellent quality and offered Jones a job at his sound system company.

Jones accepted and moved to the Twin Cities in the early 1930s. Though the company thrived thanks to Jones’s engineering prowess, Numero sold it to RCA so that he could start a joint venture with the young inventor.

In 1938, Numero founded a new venture: the U.S. Thermo Control Company. Jones served as vice president of engineering. One year later, Jones filed for Thermo Control’s first patent: the Model A, the world’s first successful system for refrigerated transportation.

Until the 1940s, transported goods were cooled by salt and ice. This created temperature inconsistencies and required manual labor. Model As were designed to be mounted onto the undersides of semi-trucks and to pass refrigerant tubing to their trailers. In the words of Jones’s patent, these tubes “condition[ed] the air” within the compartment by “tempering, humidifying and circulating.”

The Model A worked, but it was heavy and bulky. The Model B, though more compact, was not ready for intensive use. In late 1941, Jones unveiled the Model C.

Jones’ Model C was the first cooling unit mounted on the front side of a vehicle. Units fixed in this location collected less dirt than under-mounted versions. More important, the Model C’s unitary, metal body gave it the rigidity to withstand long trips and the lightness—seven hundred pounds—to save precious engine power. Running the unit were a Briggs and Stratton single cylinder engine, a Lynch Model Par S-2150 reciprocating compressor, and a six-volt starter.

The Model C was such a revolutionary invention that Thermo Control renamed itself “Thermo King” in 1941. During World War II, Thermo King made Model Cs exclusively for the U.S. military. The military applied the invention to boats, planes, and trucks in order to transport temperature-sensitive drugs and blood plasma to soldiers in need.

The Model C became commercially available after World War II and immediately made an impact on the agricultural industry. Seasonal crops could be shipped across the world. Nations could trade perishable goods. Jones’ invention laid the groundwork for the modern supermarket.

The Model C was retired from service in the mid-1960s. By then, it had made an indelible mark on international trade. L.B. Hartz Wholesale of Minnesota purchased the original Model C and donated it to the Thermo King dealership in St. Paul. Soon afterwards, the model was put on display at Thermo King’s headquarters in Minneapolis.

As of 2015, more than three quarters of the food transported in the United States ships with a refrigeration unit. The Model C has also allowed for the shipment of a variety of goods, including photographic film chemicals, flowers, and paintings.