Railroads--Chicago became the connecting point to the east, west, and south due to its location on Lake Michigan and connections to the Mississippi.
The city is the central hub for rail lines running through the country. The meat from the southern ranches came into Chicago, was processed there and then sent out. Farm crops from the Midwest were also brought through Chicago and sent through the country. Sears Roebuck was started in Chicago as well created a Midwestern hub for trade and commerce.
