Bloomington/Normal, IL, is in area code 309.
It has 7 zip codes in that city. Link for them is posted below.
Bourbonnais, Illinois, is in area code 815 and overlay code 779.
There is more than one area code. See link for Illinois area codes.
Olympia Fields, Illinois, is in area code 708.
McHenry, Illinois, has been in area code 815 since the introduction of the original area code system in 1947. On March 17, 2007, area code 779 was added as an overlay on 815.
Oak Brook, Illinois, is in area code 630 and overlay code 331.
Oswego, Illinois, is in area code 630, with overlay code 331. Oswego, Kansas, is in area code 620. Oswego, New York, is in area code 315.
Area code +1 309 is used in Bloomington, Peoria, and Moline, Illinois, USA. It includes the Illinois side of the "Quad Cities" metro area of Iowa and Illinois.(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
812 is the area code for brown county (aka Bloomington).
The 847 area code belongs to the state of Illinois. Some of the areas that are covered by the 847 area code also overlap with the 224 area code. This area code is in the upper northeast part of the state.
217 is an Illinois number
Aurora, Naperville, Illinois.