Answer to Question # 1:

It is most likely that the diagonals came first. The presence of a parallel set of diagonals, one a highway, the other a freeway, suggests that originally there was a road, presumably from central Chicago to some other city. The parallel railroad logically would have followed in approximately the same path. Then, as the city encroached on this area, the surrounding land would have been subdivided and built on. When this happened the easiest way was to use the grid. Finally, after World War II when there was a plan to build a freeway, the railroad right of way would have provided some or all of the land necessary to build the freeway, meaning that it would minimize the amount of land purchase and demolition necessary.

Question # 2:

In this view it is obvious that larger buildings follow the diagonals and the larger grid streets . Why?

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