How was Chicago's importance as a shipping center maintained?

Its all about location

Chicago is in a great location to be an island port. Its location on lake Michigan gives it access to the Atlantic ocean through the great lakes. its location near the center of the country means the goods coming through the Atlantic can travel through the great lakes before unloading in Chicago. goods from west of Chicago can be loaded onto freighters and shipped to Atlantic harbors, such as new York or ever internationally.