If you're in the market for what is "probably the oldest motorhome in the United States," you may have just found it. What was called at the time a house car, this 1917 recreational vehicle was built on a Packard base. The current owner found the old rig in California back in 1981; he moved it to Oklahoma and has since done restoration work. The original owner was a family named Pickwick from Los Angeles. The family owned and operated a bus company that later merged with Greyhound.
Here's a link to the advertisement and connections to the seller.