The telephone area code 309 serves the state of Illinois. Some of the large states covered by the area code are Bloomington, Canton, Galesburg, Macomb, Moline, Normal, Pekin, Peoria and Rock Island. Some of the smaller areas or communities covered are within the western part of central Illinois.

The region which is covered by this particular area code ranges for the whole of southern and central parts of the state. The counties and cities which are covered by this area code are as under.

Abingdon, Adair, Alba, Albany, Aledo, Alexis, Allentown, Allin, Alpha, Alta, Altona, Anchor, Andalusia, Andover, Annawan, Appleton, Armington, Arrowsmith, Astoria, Atkinson, Avon, Babcock, Banner, Bardolph, Barnes, Barstow, Bartonville, Bath, Bell plain, Bellevue, Bellflower, Bellview, Benson, Bernadotte, Berwick, Beverly manor, Biggs, Biggsville, Birmingham, Bishop, Bishop hill, Blackhawk, Blandinsville, Bloomington, Bloomington heights, Bloomington normal airport, Blyton, Boden, Bowling, Boynton, Bradford, Bradley univ, Breeds, Brereton, Brimfield, Broadmoor, Bryant, Buda, Buffalo pr, Buffalo prairie, Burt, Bushnell, Byron hills, Cable, Cambridge, Cameron, Camp grove, Campbells island, Canton, Carbon cliff, Carlock, Carman, Carthage lake, Castleton, Caterpillar inc, Cazenovia, Ceffco, Central, Check row, Chillicothe, Cleveland, Coal valley, Coe, Colchester, Colfax, College hills mall, Colmar, Colona, Columbia heights, Congerville and Cooksville.