What is 773 area code?

The 773 area code is a telephone area code in the North American Numbering Plan (NANP) for the U.S. state of Illinois. It covers the city of Chicago, excluding the downtown area and some adjacent neighborhoods, which are served by the 312 and 872 area codes.

Here are some key points about the 773 area code:

1. Introduction and Geography: The 773 area code was introduced on October 12, 1996, when it was split from the 312 area code due to the growing demand for telephone numbers in the Chicago metropolitan area. The split was necessary because 312 was running out of phone numbers.

2. Coverage: It services the surrounding areas of the Loop in Chicago, essentially covering the residential sections and some business areas excluding downtown. It's mostly on the north, northwest, and southwest sides of Chicago.

3. Overlap: In 2009, an overlay plan was introduced with the 872 area code, which was implemented to provide additional numbers for the same geographic area as both 312 and 773. This means that new telephone numbers may have either the 872 or 773 area code, but they serve the same geographic area.

4. Dialing: Due to the overlay, ten-digit dialing (area code + phone number) is mandatory for making local calls within this area. This applies to calls that might have been local with seven-digit dialing before the overlay.

5. Usage: The 773 area code is common for residential and business phones in Chicago, and like many other urban area codes, it has seen heavy usage as the city's population and the demand for new phone lines have increased.

Overall, 773 is one of the several area codes serving the bustling city of Chicago, reflecting its status as a major U.S. urban center.