"The Lincoln Highway started it all for the automobile," said Paul Gilger, president of the California chapter of The Lincoln Highway Association, who is leading the tour from San Francisco.
"Before that, people traveling outside of their town did so on a train."
The highway - the precursor to Route 30 in Pennsylvania and to America's highway and interstate system - in a sense marked the birth of trucking.
Before its creation, people primarily ate only what was grown or raised near them, he
"No one in Ohio had ever seen an avocado," Gilger
A few areas remain much as they did 100 years ago, such as unpaved stretches in the Utah desert, Gilger
"There's no telephone poles; there's no cellphone service; there are no signs," he