Railroads, steamships, and canals were marvels of food transportation in the nineteenth century. In the twentieth century, that honor belonged to the highways. Construction of a national highway system in the United States began in 1883. By 1910 one thousand miles of concrete road had been constructed. Twenty years later 694,000 miles of surfaced roadway and well over a million trucks crisscrossed the country. In 1932 U.S. Route 66, a 2,200-mile highway linking Chicago with Los Angeles, opened.
After World War II fundamental changes were made in food transportation by road. The Federal-Aid Highway Act of 1956 authorized the construction of a 41,000-mile interstate highway system. By 1976 approximately 38,000 miles of the Interstate Highway System were open, enabling trucks to carry foodstuff shipments once reserved for railroads. Gasoline prices fell, decreasing the cost of transporting food by road. Accompanying the rise of food transportation were technologies that enabled long-term storage. Major innovations in refrigeration after World War II gave birth to the frozen food industry. Scientists developed controlled-atmosphere techniques for controlling the ripening of—and thus extending the shelf life of—fruits, vegetables, and other perishables. With the new techniques, iceberg lettuce, developed to be almost indestructible in any form of transportation, could be vacuum-cooled in transit. Ethylene was introduced so that tomatoes could ripen during transport rather than on the plant.