After one month of building pre-production models, Ford cranked up the line in earnest on Monday, March 9, 1964. In the early months of production, the Rouge built both Mustangs and midsize Fairlane sedans. Soon however Mustang demand prompted Ford to move Fairlane production to another plant and dedicate the massive Dearborn factory to Mustangs only. 

In July 1964, Ford also began producing Mustang at the San Jose, CA plant followed a few months later by the plant in Metuchen, NJ. 

Today, Mustang is again built alongside Ford's midsize sedan, although that is now the Fusion and it happens a few miles away in Flat Rock.?