Joseph Numero and Frederick Jones patent the first transport refrigeration unit, the "Model A," in 1938. This landmark invention ushered in the era of frozen foods, large supermarkets and the restaurant industry, as we know it today. Refrigerated transport also made the delivery of fresh produce anywhere in the country a possibility, no matter what the season.

The introduction of diesel engines in refrigerated units in 1958 by Thermo King was a big step for many reasons, with the main benefit being extended engine life as compared to gas-powered units. Where a gas-powered engine had an expected life of 5,000 hours, a diesel-powered engine could run up to 25,000 hours, allowing great savings in engine maintenance and replacement. This development also fed the rapidly growing long-haul trucking industry, where the long trips with high run hours no longer necessitated the frequent replacement of engines.

In 2003 Thermo King introduced the MAGNUM reefer unit, the only reefer unit on the market that maintains a -35 degrees C (-31 degrees F) set point. The MAGNUM guarantees that deep- frozen cargo will stay frozen even in 50 degree C ambient conditions. This development is particularly important for high-value loads like seafood, where a constant -35 degree temperature is necessary to ensure that the quality of the load is maintained for customers.

Today, Thermo King Corporation manufactures transport temperature control systems for a variety of mobile applications, including trailers, truck bodies, buses, shipboard containers and railway cars.