By 1900, the automobile was a new-fangled technology that was here to stay. Its evolution as a military vehicle was not truly to be experienced until World War 1 (1914-1918) which helped to further all manner of technologies that changed the world thereafter. Prior to the war and before the turn of the century, thought was already being given to mechanized warfare taking the place of cavalry units - this in the form of armored cars.
Once such development was the 1898 "Davidson-Duryea Gun Carriage", a rather simplistic-looking three- or four-wheeled design by today's standards that incorporated seating for up to four, mounted an M1895 Colt-Browning machine gun behind a large metal shield and was powered by a gasoline engine. While not adopted by the U.S. Army, the car did go on to influence future use of mechanized vehicles marking its developer, Royal Page Davidson (1870-1943), as a pioneer of this type in American military history.
The general design of the Davidson car was then evolved in the follow-up 1900 work that produced the "Davidson Automobile Battery". This vehicle ditched the gasoline engine of the original, due to poor power output, and installed a steam-based boiler arrangement in its place. A 4x2 wheeled configuration was standardized and the vehicle retained its seating for four. The machine gun was still fitted ahead of the front passenger with the optional armor shield. The passengers in the rear seats faced rearwards and could serve as shock troops or scouts by disembarking the vehicle when needed. In their place, cargo could also be carried. Construction of the new vehicle was headed by both Page military cadets based at the Northwestern Military and Naval Academy of Highland Park, Illinois. Two vehicles were completed for 1901 and were known simply as "Number 1" and "Number 2".
In military service, the car would be have been suitable as a reconnaissance vehicle capable of ferrying its observers to and from the frontlines. Protection would be through the inherent armor scheme as well as the 0.30 caliber machine gun which gave its operator a 180-degree angle of fire to either side over the front. Despite their revolutionary nature, the Davidson Automobile Battery armored car was - too - never adopted, armies continuing support of their cavalry units for the interim.
In 1915 - prior to American involvement in World War 1 - Page and his cadets put together the Davidson-Cadillac Armored Car. The design marked the first dedicated armored car vehicle in the United States.