Although PORTABLE LEVITTOWN pertains specifically to the American house trailer of the mid-20th century, their early evolution does merit at least a perfunctory mention.
The history of the camping trailer and mobile home can be traced back to the Gypsy caravans of Europe and, specifically, to the American Conestoga Wagon, whose first recorded mention dates back to 1717.
Named after the Conestoga River in Southeastern Pennsylvania, these horse-drawn vehicles were used to settle Western Pennsylvania, Ohio and sections of Eastern Canada in the late 18th and early 19th centuries.
The typical Conestoga Wagon was 18 feet in length and 4 feet in width. Its bottom was curved to keep cargo from shifting or falling out. The average speed of this mode of transport was 15 miles per day.
Drawing from Wikipedia / Achive of Pearson Scott Foresman
The world's first so-called leisure travel home made its debut in Great Britain, in 1885. Known as The Wanderer, it was built for Scotsman William Gordon Stables, a well-known doctor and author. Mr. Stables used The Wanderer to travel throughout Great Britain. He published his exploits in his 1891 book, "The Gentleman Gipsy".
William Gordon Stables (on the right) poses in front of The Wanderer. The horse-drawn abode was 30 feet long and 7 feet wide. It was appointed in the most opulent of Victorian decor.
Photo from www.caravanclub.co.uk