The first auto body designers and builders represented what was already an old established craft.
People had been traveling in wheeled carriages for hundreds and hundreds of years. But at the dawn of the 20th century, they would be powered not by horses or some other draft animal, but by some sort of motive power. It mattered little to early body builders if vehicles were propelled by a gasoline engine, electric power or steam. Their task was to create a conveyance that would carry people---period. The body builders contended that if the carriage designs of the late 1800s were good enough for horses, they were good enough for engines. And so it was that wood was the first automotive substrate.
One of the earliest references to an automotive body comes from the story of a doctor in Youngstown, OH. In June 1895, Dr. Carlos Booth experienced a runaway situation with his wagon and team of horses. Not wanting to experience that again, he designed a motor vehicle and commissioned a local shop to build it. Among its many features was a “body designed to hide the engine and the mechanisms of the vehicle.” (This is perhaps the earliest reference to an automobile body that served primarily as an aesthetic portion of the vehicle.) He is purportedly the first doctor in American to make house calls in a motor vehicle. It’s unknown if his car ever needed body work.
A short time later, in 1897, a car named the Hugot hit the street with a wicker body. It was certainly light-weight. The bad news was it couldn’t take much of a hit.
The first U.S.- built auto to use a steel body (in the midst of a world of wooden bodies) was the 1901 Eastman Steamer. The first to have an aluminum body was the 1902 Marmon. Both the Eastman and Marmon were built with all-wood frames to which metal panels were pinned. For the most part, cars were primarily made of wood or wood and some steel. The wooden body panels of those early cars restricted body designers. Wood can only be steamed and bent into simple curves. When applied to wooden frames, the body panels of one make of car looked pretty much like those of any other make. When sheet steel and aluminum came along, this sameness in appearance started to change.