The telephone country code for the United States is +1. The area
codes for Illinois are: 217 = Springfield, Champaign;
224 = (overlay of 847);
309 = Bloomington, Peoria, Quad Cities;
312 = downtown Chicago;
331 = (overlay of 630);
447 = (planned overlay of 217);
618 = East St. Louis, Collinsville;
630 = Aurora, Hinsdale;
708 = Cicero;
730 = (planned overlay of 618);
773 = Chicago (outside downtown);
779 = (overlay of 815);
815 = Rockford, Joliet;
847 = Roselle, Northbrook, Elk Grove Village;
872 = (overlay of both 312 and 773).