One of the earliest purpose-built facilities was the Albert Kahn-designed Detroit Arsenal, located in suburban Warren, MI, literally across the street from the future site of the General Motors Technical Center. Built by Uncle Sam, the plant churned out M3 Grant and M4 Sherman tanks with frightening speed, but it wouldn't have been possible without Chrysler. The company (which is ironically now allied to a former supplier of Nazi Germany and fascist Italy) operated the plant and applied automotive mass-production techniques to producing the government-designed tanks.
The plant was so successful, according to Fiat Chrysler historian Brandt Rosenbusch, that it singlehandedly outpaced the entire Third Reich's tank production by 5,000 units over the course of the war. The Detroit Arsenal was also responsible for a quarter of all American tank production during the war. And like so many wartime factories, women formed a large percentage of the workforce, as men were drafted out of assembly work and into the armed forces.
Chrysler has commemorated the 75th anniversary of the Arsenal of Democracy speech with a video on the Detroit Arsenal and its role there. And as for the site today? It built tanks up until 1997, and still serves as the home of the US Army's TACOM (Tank-automotive and Armaments Command) Life Cycle Management Command, a major site for tank research and development.