Mail-order business.
Founded in Chicago in 1872 as the world's first general-merchandise mail-order catalog business, Montgomery Wards (now known as Wards), is one of the United States' largest privately held retailers.

First nuclear chain reaction.
On December 2, 1942, Enrico Fermi, let the world know the Atomic Age had arrived. It happened at a squash court under the football stadium at the University of Chicago.

First skyscraper.
The nine-story steel-frame Home Insurance Building (which no longer stands), was built in 1885, after the Chicago Fire of 1871, when the building of wooden structures was banned by the Common Council.

First Planetarium.
The Adler Planetarium in Chicago was the first planetarium in the Western Hemisphere.

First nuclear reaction.
The University of Chicago became the site of the world's first atomic reaction.

Ferris Wheel.
The first Ferris wheel made its debut in 1893 at the World's Columbian Exposition in Chicago.

World Cup Soccer championship in the United States.
In 1994, the first game and the opening ceremonies of the first World Cup Soccer championship ever to be hosted in the U.S. were held in Chicago.

Other Chicago Firsts:

Steel frame skyscraper, 1885
Softball, 1887
Elevated railway, 1892
Zipper, 1896
Daytime TV soap operas, 1949
McDonald's Restaurant, 1955
Electric iron and cooking range
Grain reaper
Reactor to produce electricity from atomic energy
Bifocal contact lens
Winding watch