RV History with Al Hesselbart
Popular selling features of RVs today, such as slide outs, are much older than most RVers realize. Almost every RV feature inside motorhomes, trailers and fifth wheels (other than furniture and appliances) was known before 1920. Modern rigs seem to require slide outs as a selling feature; nobody wants an RV without one (or multiple).

Additional options for the apartment included a shower with water supplied from a bladder that was laid on the roof (and then filled once in position). The water was heated by using a hose routed through the radiator with heat provided by the engine. A canvas curtain surrounding the showerhead protected privacy.
Since radio and TV ads had not yet been conceived, and RV travel magazines were unknown, advertising for this (and other early RV creations) was distributed in magazines, such as Popular Science, in which photos similar to the above were seen in a 1916 edition.