The American Army was slow to appreciate the armored car as a viable battlefield instrument in the fighting of World War 1 (1914-1918) and the vehicles of U.S. origin were all deployed stateside by National Guard units and local security forces during the conflict. It was the Untied States Marine Corps that led the way with the purchase of eight "King Armored Cars" (detailed elsewhere on this site) and future Army General George S. Patton championed mechanized warfare as early as 1916, proving its value during the Mexican Punitive Expedition in the hunt for Pancho Villa. At the end of the war, and into the 1920s, there proved little further development in the field for the Army.
Some experimentation did take place even during The Great War period but these mainly ended as "one-offs" or limited production efforts donated or sold to local forces across the country. In the end, all suffered from the same limitations: being built upon a commercial truck or car chassis, weighed down by its armored superstructure and armament, and lacking strong cross-country mobility due to slim tires and overall weight. Into the 1930s, thought was, once-again, though given to design and development of armored cars by the American Army and one of these ventures produced the short-lived "M1 Armored Car".
The vehicle began life as the "T4 Medium Armored Car" built primarily by James Cunningham, Son and Company of Rochester, New York. An all-new four-wheel articulating bogie arrangement was used to better equip the rear paired axles. An angular armored superstructure was dropped over the six-wheeled chassis which featured a driving compartment at midships and a turret set over the rear section (the engine was housed in the bow as usual). The turret was brought along by engineers at the Rock Island Arsenal and designated the "T5", armed with a 0.50 caliber M1921 Heavy Machine Gun (HMG) coupled with a 0.30 caliber M1918 Medium Machine Gun (MMG) installed coaxially. Another 0.30 cal MMG installation was optional at the turret roof as an anti-aircraft measure.
The vehicle was crewed by four personnel and was powered by a single 8-cylinder gasoline-fueled engine developing up to 133 horsepower. Suspension was across the 4x6 wheeled arrangement in which drive power was granted to the two rear axles and steering accomplished with the front axle. The vehicle could make road speeds of 55 miles-per-hour and range out to 250 miles in ideal conditions (namely prepared, paved roads). Spare tires were situated along the front sides of the hull, elevated for ground clearance. Dimensions included a running length of 15 feet, a beam of 6 feet and a height of 6.9 feet. Weight reached just over 5 tons.
Two T4 "pilot" (prototype) vehicles were constructed and these were evaluated at the famous Aberdeen Proving Grounds in Maryland before being delivered into the hands of the Cavalry Board of Fort Riley (Kansas). From there, they were handed to the men of Troop A, 1st Armored Cavalry Squadron of Fort Bliss. Testing ultimately spanned from 1931 until 1933/1934 to which the type was accepted into formal service as the "M1 Armored Car" - the first standardized armored car design taken on by the U.S. Army. Twenty of the cars were contracted for but, due to natural Army budget constraints and the pressures of the Great Depression, just twelve were completed with most of the lot furnished by the Rock Island Arsenal.
While a promising venture, the M1 Armored Car was not a complete success: it still lacked the needed cross-country mobility as its front axle was unpowered and the sheer weight of the vehicle meant it could easily become bogged down in soft terrain. Its overall length also required a significant turn radius and armor protection was only good enough against small arms fire. The vehicle was also tall making it a tempting target on the horizon, particularly for enemy tanks, artillery crews, and machine gunners. The armored superstructure also limited vision for its crew, as did the long nose section for the driver.
Despite this, the M1 Armored Car served as a crucial stepping stone to the better Army designs witnessed in World War 2 (1939-1945) and also helped to flesh out the near-future of American mechanized warfare doctrine which would be mightily called upon in the upcoming war. The age of the "classic" armored car of the World War 1-era was more or less over and the M1 Armored Car lasted in service up until 1939 - the start of the war in Europe.