S-Helper S Scale 35' Dry Van Trailer, Canadian Pacific/CP

A Scottish-American engineer named Alexander Winton is credited with inventing the semi trailer in Cleveland, Ohio. He was an automobile manufacturer and wanted to get his cars to customers without putting any miles on the vehicles. Winton designed a car-hauling unit that could be pulled by a truck, and soon, other car manufacturers were purchasing his semi-trailer product to transport their vehicles.

The use of “tractor-trailers” increased dramatically during World War I, when the military found that they offered speed and flexibility not available with trains and horse-drawn trailers. This was especially true after inflated (pneumatic) tires were created, as they addressed concerns about the effects steel and solid rubber wheels were having on the dirt and gravel roads of the day. 

In the 1930s, the expanding construction of paved roads made semis even more useful, and when the Interstate Highway System was developed in the 1950s and 1960s, the tractor-trailer became the cornerstone of the cargo transportation industry.

TOFC Service (Trailer On Flat Car) started in the early 1950s when railroads converted flat cars to carry trailers. Many 40’ and 50’ flatcars were used for this service, although some railroads used boxcar frames to make new flatcars. Prior to 1958, most trailers east of the Mississippi River were restricted to 35’. These trailers could easily fit onto the 40’ and 50’ converted cars, and some railroads started to develop 75’ flatcars to carry two trailers.

In 1958 Federal Law allowed 40’ trailers nationwide. As trailers grew longer, so did the railcars, and the shorter flatcars and trailers began to be phased out of TOFC service.