Cities like Milwaukee and Chicago appear as dots, or points, on a map or plane. When dots are connected, they form a network, and the points are called nodes in the network. Look at the map below. It shows both the idea of dots, or points, as a location and the idea of points as nodes in a network. Networks are sometimes called graphs, and the geometry of graphs is called graph theory.
The city is located in the East North Central Region on the southwestern tip of Lake Michigan. The Chicago and Calumet rivers are the city's main rivers. Downtown Chicago seen from the John Hancock Center observatory, looking south.
