By 1850, the Galena and Chicago Union Railroad (after that, the Chicago & Northwestern and now Union Pacific) was constructed as far as Elgin, Illinois, and passed through the settlement area. In the 1850s the land on which Oak Park sits was part of the new Chicago suburb, the town of Cicero. The population of the area boomed during the 1870s, with Chicago residents resettling in Cicero following the Great Chicago Fire of 1871 and the expansion of railroads and street cars to the area. "In 1872, when Oak Park received its own railroad depot on the Chicago and Northwestern Railway, its rapid emergence as a residential suburb of Chicago began. In 1877, the railroad was running thirty-nine trains daily between Oak Park and Chicago; in the subsequent year, more railroads and street car lines, with increased service, came to link Oak Park and Chicago. As Chicago grew from a regional center to a national metropolis Oak Park expanded – from 500 residents in 1872 to 1,812 in 1890, to 9,353 in 1900, to 20,911 in 1910, to 39,585 in 1920. Oak Park thus emerged as a leading Chicago suburb."