Effingham is a city in and the county seat of Effingham County, Illinois, United States. The population was 12,604 at the 2015 census estimate. The city bills itself as "The Crossroads of Opportunity" because of its location at the intersection of two major Interstate highways: I-57 running from Chicago to Miner, Missouri, and I-70 running from Utah to Maryland. It also is served by U.S. Route 45, which runs from Ontonagon, Michigan to Mobile, Alabama, U.S. Route 40, the historic National Road, which stretches from Atlantic City, New Jersey to Summit, Utah, and Illinois Route 33 and Illinois Route 32 also run through the city.