Many years ago Midwestern cities grew before manufacturing of automobiles and similar heavy industrial output. Here is an excerpt from Cities of the Heartland: The Rise and Fall of the Industrial Midwest by Jon C. Teaford:
At the same time Milwaukee residents were profiting from the tanning of animal hides. The tanning business thrived in Milwaukee not only because of plentiful hides from nearby packing houses but also because of the city's proximity to the chief sources of hemlock bark in Wisconsin and Michigan. The eastern states had already exhausted this supply of this bark which was a vital ingredient to the tanning process. Consequently, tanneries gravitated westward, and by 1886 Milwaukee boasted of fifteen tanning establishments employing one thousand people.
As you can see the migration of industries often follows the path of least resistance. So tanneries migrated west to follow the supply of hemlock bark. Today there are still tanneries in Wisconsin, but
Increasing competition from abroad, however, led to the industry's
decline in the U.S. and by the end of the 1930s, only the strongest
firms remained in production. Milwaukee remains prominent in leather
production but tanning plays only a minor role overall in local
The economies of cities and regions continues to change, as they always have. The challenge is for cities like Milwaukee and Chicago to adapt to new times and embrace the change. Clinging to old times and old economies is a recipe for disaster.