The first attempts at commercial armored trucks were inspired by the combat success of military armored cars in World War I.
In 1920, a Chicago area adelivery company called Brink's started converting school buses into security vehicles by attaching steel plates to the lower body panels and barring the windows. Each bus was followed by a Model-T automobile filled with armed guards.
The first true commercial armored car was built that same year in Minneapolis, Minnesota, for a St. Paul police chief turned private detective Mike Sweeney. Sweeney designed the car and put it into service for his Sweeney Detective Bureau.
Early armored cars only wore steel plating on their body panels; they retained the wooden floors of the truck chassises on which they were built. This ended in 1927 when thieves buried explosives in the road and blew up a Brink's truck carrying $100,000 in payroll money.