Carbondale is a city in Jackson County, Illinois, United States, within the Southern Illinois region informally known as "Little Egypt." The city developed from 1853 because of the stimulation of railroad construction into the area. Today the major roadways of Illinois Route 13 and U.S. Route 51 intersect in the city. The city is 96 miles southeast of St. Louis, Missouri, on the northern edge of the Shawnee National Forest. Carbondale is the home of the main campus of Southern Illinois University.As of the 2010 census, the city had a population of 25,902, and it is the state's 20th-most-populated city outside the Chicago Metropolitan Area. In addition, the city is the most populous in Southern Illinois outside the St. Louis Metro-East region, and the most populous city in the Carbondale-Marion-Herrin, Illinois Combined Statistical Area. The CSA has 126,575 residents, the sixth-most-populous Combined statistical area in Illinois.