Via Curbed Chicago, a Canadian start-up, Cube Cities, used commercial real estate data to create an animation depicting the construction of Chicago's skyscrapers. (Unfortunately, it seems to begin with an inaccuracy: the Union League Club of Chicago was founded, sort of, in 1862, but its building at 35 W. Jackson, which appears to be the one in the animation was built in 1926. Otherwise the noted buildings seem to check out.)

What's interesting about it is the patterns—a riot of building in the roaring '20s, a slowdown during the Depression, an explosion of tall skyscrapers in the 1960s and 1970s after SOM engineer Fazlur Khan pioneered the framed tube system of building construction, beginning with the DeWitt-Chestnut building in 1965. It's best appreciated in full-screen mode.