When the United States put into effect its own area code telephone system (known as the North American Numbering Plan) back in 1947, the majority of the countries got only one area code. However, some countries received more than one – Illinois got four area codes, Texas also got four, while New York received five area codes. In the beginning Illinois had just four area codes: 312 that covered all of Chicago, 815 for northern Illinois, 217 for central Illinois and 618 that covered southern Illinois.
The country didn’t get another area code until 1957, when 309 was added to serve western central Illinois.
Nonetheless, by the late 1980s, Illinois was completely exhausted and had run out of possible numbers, which meant that new area codes were necessary to meet the demands of the growing population. Today the state of Illinois has 13 area codes, 9 standard and 4 overlay codes. Read on to discover some fun facts about Illinois’ area codes.
1. Area code 312 is one of the original area codes created in 1947 and in the beginning it served the entire Chicago area. Today this area code serves only downtown Chicago, including the Chicago Loop and its surrounding areas.
2. 312 is one of the smallest area codes by size in the United States, because it covers just a few square miles.
3. Area code 217 is the telephone area code for western and central Illinois regions including Urbana, Champaign, Quincy, Decatur, and Springfield. It was created in 1947 and originally covered the Metro East region of Illinois. 447 was added in 2021 as an overlay area code to 217.
4. Area code 309 was created in 1957 and serves the central-western region of Illinois including Bloomington, Moline, Pekin, Rock Island, Peoria, Canton, etc.
5. 309 also serves 18 counties and numerous small communities in the state of Illinois.
6. Another fun fact about 309 is that it was the only new area code created in Illinois between 1947 and 1989.
7. 708 was split off from area code 312 and officially put into use in 1989. Today, this area code serves the southern and the inner west suburbs of Chicago, including Chicago Heights, Oak Lawn, Oak Park, and Orland Park.
8. 708 served almost every suburb of Chicago for seven years, until it was split to create the two area codes 630 and 847.
9. Area code 773 was created in 1989 with the intention to relieve area code 312 which was near exhaustion. It covers the city of Chicago, with the exception of the Downtown Chicago Loop region which is covered by 312.
10. Even though 773 was created and officially put into use in 1996, the residents of Chicago were given a three-month grace period before they needed to use the new area code.
11. Area codes 630 and 331 serve the west suburban areas of Chicago in DuPage County and Kane County, including Aurora, Naperville, and Wheaton.
12. 630 was created from a split of area code 708 in 1996. However, due to the extensive growth of the Chicago suburbs, after a few years 630 was nearly exhausted. That’s why 331 was added as an overlay code to 630 in 2007.
13. 618 is an early North American area code created in 1947. It serves southern Illinois, including Belleville, Carbondale, Marion, Alton, Salem, and most of the Metro East region of St. Louis suburbs in Illinois.
14. 618 is the only one of the four original area codes of Illinois that has never been split or overlaid.
15. Area codes 815 and 779 cover a big portion of northern Illinois outside the Chicago and Quad Cities regions. But, they also cover numerous southwestern, outer western, and northwestern suburban areas in Chicago.
16. 815 is another original North American area code since 1947, while 779 is an overlay code to 815 since 2007.
17. Illinois’ area codes 847 and 224 cover the north and northwest suburbs of Chicago including Lake County, northern Cook County, a part of McHenry County, as well as northeastern Kane County.
18. 847 was created in 1996, while 224 was created as an overlay to 847 and put into use in 2002.
19. 872 is the overlay of area codes 312 and 773 and covers the city of Chicago. It was officially put into service in 2009 and with the implementation of this area code, all local calls in Chicago must be dialed with the 11-digit phone number.
20. 872 is the third overlay area code in this region and the tenth code that serves northeast Illinois.