On June 29, 1889, voters in four incorporated townships surrounding Chicago went to the polls and decided to become part of the City of Chicago, eliminating their local unit of government and boosting the city’s population by 225,000 people. The expansion made Chicago the nation’s second largest city by population, surpassing Philadelphia.

The addition of Hyde Park Township and Lake Township on the South Side and Lake View Township and Jefferson Township on the North Side added 125 square miles to Chicago’s size, making the city the nation’s largest by physical size at that time.

Learn more:
Annexations and Additions to the City of Chicago – Encyclopedia of Chicago
Gulp! How Chicago gobbled its neighbors – WBEZ