From the late nineteenth century to the present day, the U.S. auto industry has been concentrated in the Midwest. The vast majority of production facilities are concentrated in the so-called “auto corridor,” a region extending from Michigan and Chicago, Illinois in the west, south and east through Indiana, Ohio, and Pennsylvania, and north into Ontario, Canada. The availability of raw materials in the Midwest makes the region a natural hub. Over the last twenty years, the concentration of the U.S. auto industry in this region has increased; assembly plants formerly located on both coasts have been replaced with new plants built in the Midwest to minimize distribution costs. The increasingly lean and efficient just-in-time distribution process allows suppliers to deliver parts and materials to multiple assembly plants.