Thermo King put an automatic refrigerator on the truck so the cold travels with the cargo.

In the summer of 1938 Joseph Numero was out with a friend in the shipping business when the friend got a call: a whole truckload of chickens had overheated on a long trip and been lost. Refrigeration existed, but it lived in icehouses and at depots; it did not travel with the cargo over the road.

Numero took the problem to Frederick McKinley Jones, his partner and engineer. Instead of building better central cold stores or hauling more ice, they put a small automatic cooling unit directly on the hauling vehicle, powered by the truck. Any truck or railcar could now keep its own load cold mile after mile.

The result was Thermo King, described as the world's first automatic refrigeration system for trucks and railroad cars. It let perishables move from farm and packer to town without a break in the cold chain, and it let a carrier run any route rather than only routes near an icemaker.

Jones and Numero later won the National Medal of Technology for refrigeration systems used in trucks, trailers, boxcars, ships and planes; Jones alone took out more than 60 patents.

Put the refrigerator on the truck so cold rides along.

A portable unit uses the vehicle's own power, so cold is created along the route instead of fetched from an icehouse.

Mounting refrigeration on the vehicle makes every truck a cold chain, not just ones parked near a cold-store depot.

It standardizes refrigerated road freight, so a carrier can serve any route and any perishable cargo.

When the bottleneck is a resource that only exists in a few fixed places, put the resource on the moving asset instead of building more fixed depots.

Thermo King became the foundation of the transport-refrigeration industry, and Jones was inducted into the American Truck Historical Society Hall of Fame in 2024. Refrigerated trucks and trailers now carry much of the world's perishable food, making the portable unit a quiet pillar of the modern cold chain. The design principle — carry the cold generator, not the cold — remains the default for road freight.