Chicago

Chicago sits at the southwestern corner of Lake Michigan, on the flat plain where the Great Lakes very nearly meet the Mississippi River watershed. That accident of geography made it the great hub of the American interior: a low portage between lake and river systems let early traders cross from the Atlantic-bound Great Lakes to the Gulf-bound Mississippi, and railroads later converged on the same spot from every direction. The third-largest U.S. city grew at this continental crossroads.

The land is almost perfectly flat — old glacial lakebed — which let the city expand in an orderly grid and made it a natural rail and shipping center for grain, lumber, and livestock. Engineers famously reversed the Chicago River in 1900 so the city's sewage flowed away from its lake drinking supply, toward the Mississippi instead. The lakefront, lined with parks and beaches, faces an inland sea so large the far shore is invisible.

Chicago's position as the hinge between East and West, lake and river, built it into the industrial and transportation capital of the Midwest and the birthplace of the skyscraper. It still anchors a metro of more than nine million on the shore of Lake Michigan.