The pickup truck has existed for a long, long time. In the early years, a pickup truck denoted a vehicle with an aftermarket pickup bed attached to a factory-built chassis/cab. Apparently, the first actual factory-built pickup truck was built by the Ford Motor Company, in 1925, near the end of the Model T’s long run.
http://www.curbsideclassic.com/curbside-classics-american/curbside-classic-1930-ford-model-a-pickup-the-modern-pickup-is-born/