Area code 872 is an overlay for both 312 and 773, covering all of the city of Chicago, Illinois. It was introduced in 2009 to address the growing demand for new numbers in the urban center. The code spans downtown Chicago, known for its iconic skyline, financial institutions, and corporate headquarters, as well as the outlying neighborhoods that define the city’s diverse and vibrant culture. Ten-digit dialing is required throughout. While 312 and 773 carry more cultural weight, 872 is now a common code for mobile and business numbers, supporting continued growth in one of America’s most important metropolitan cities.