309 Area Code: Peoria, Illinois

West-central Illinois is served by the 309 area code, with Peoria as its primary city. Peoria sits along the Illinois River where it broadens into Peoria Lake, in a stretch of the river valley that has long supported heavy industry — agricultural equipment, river commerce, and food processing among the largest. Caterpillar's long-running presence in the region anchored much of the local economy through the twentieth century, and the city's working profile continues to reflect that manufacturing base alongside healthcare, higher education, and a substantial service sector. The 309 footprint reaches through Bloomington-Normal, the Quad Cities' Illinois shore, and Galesburg out toward the Mississippi.

Other Illinois cities — Aurora, Belleville, Chicago, and Cicero — recur in the directory's records linked to 309 numbers. None are inside the 309 footprint. The pattern reflects standard public-record dynamics, with phone numbers porting across Illinois and addresses linked across multiple cities. The directory currently documents 471 distinct prefixes within 309 in detail, a working subset of the prefix population the code carries.

Peoria's home values come in well below the US median, in line with broader downstate Illinois pricing. Median household income runs below the national figure, the city's median age sits a few years under the US reading, and population places Peoria as one of the larger downstate cities — substantial in its regional context but well behind the Chicago-area metros further north. The 309 footprint as a whole reflects a mix of mid-sized cities, university towns, and agricultural counties spread across west-central Illinois.