I saw this 1928 truck popup and was thinking it might be the start of Popup truck camping. Top speeds started getting to where popups made sense. Anyway, the whole roof pops and I've never seen a older popup. I think it's really cool.
http://www.flytecamp.com/vintage-restoration/item/1928-ford-house-car
http://www.flytecamp.com/vintage-restoration/item/1928-ford-house-car