It predates similar van styles by decades.

So, you think you’re on-point when it comes to automotive history? We aren’t talking performance history or cool stuff like that. Anyone can rattle off the development of the DOHC engine or the first Ferrari road car (the 125 S in case you’re wondering). When it comes to utilitarian knowledge such as, say, the first sliding door used on a vehicle, things aren’t quite as well known. Citroën would like to change that.

The automaker has a social media series called Story Time that features short-fire video clips about vehicles from its illustrious past. One of those is a commercial van lovingly named the TUB, built from 1939 though 1941 upon which production stopped because of a small conflict called World War II. The design certainly has a Citroën vibe about it, but this commercial transport vehicle was actually a precursor to many modern vans.

More importantly for this article, it’s the first to feature a sliding side door. Similar to vans that would follow decades later, the TUB had a large door on the right side that slid straight backward for easy access into the cargo area. It was also front-wheel drive with greenhouse positioned all the way at the front. It’s a shape that would eventually define vans for generations.

It should be noted that the video states the TUB was the first vehicle of its kind to feature such a door. The evolution of work vehicles in those days primarily consisted of truck-styled machines through the 1920s and 1930s, giving birth to the classic saloon delivery platform. As you might imagine, there isn’t much in the way of information on such obscure factoids so we will take Citroën at its word that the TUB was indeed the first. At the very least, this should get you some major points during auto trivia night.