Area code 312 is the original area code for downtown Chicago, Illinois, and one of the most iconic codes in the United States. Established in 1947, it once covered the entire Chicago area but has since been reduced to only the central business district. In 1996, it was overlaid with area code 773, and in 2009 with 872, to meet the demand for new numbers. The 312 code is synonymous with Chicago’s core, including the Loop, Magnificent Mile, and major corporate headquarters. It’s a symbol of prestige and often used in business and cultural branding. Ten-digit dialing is required, and 312 remains a badge of legacy and urban sophistication in the heart of the Windy City.