High Quality Content by WIKIPEDIA articles! Oak Park, Illinois is a suburb bordering the west side of the city of Chicago in Cook County, Illinois, United States. It is the twenty-fifth largest city in Illinois. Oak Park has easy access to downtown Chicago (the Chicago Loop) due to public transportation such as the Chicago 'L' Blue and Green lines, CTA buses, and Metra commuter rail. As of the 2000 census, the area had a total population of 52,524. A census estimate for 2003 showed that the population had dipped to 50,824. In 1837, Joseph Kettlestrings purchased 172 acres of land just west of Chicago. By 1850, the Galena and Chicago Union Railroad was constructed as far as Elgin, Illinois, and passed through what would later become Oak Park. In the 1850s the land on which Oak Park sits was part of the new Chicago suburb of Cicero, Illinois. The population of the area boomed during the 1870s, with Chicago residents resettling in Cicero following the Great Chicago Fire of 1871.