331 Area Code: Aurora, Illinois

Illinois's 331 area code is an overlay layered onto the same west suburban Chicago footprint long served by the 630. Aurora anchors the directory's records here. The city sits on the Fox River roughly forty miles west of downtown Chicago, organized around a working downtown that retains a substantial cluster of late-nineteenth-century buildings and a casino on the river. The 331 footprint reaches through Naperville, Wheaton, Oak Brook, and the broader cluster of DuPage and Kane County communities that fill out the western suburbs.

Records linked to 331 numbers in the directory often include Belleville, Chicago, Cicero, and Peoria — Illinois cities outside the 331 footprint. The pattern reflects standard public-record dynamics, with phone numbers porting across Illinois and addresses linked across multiple cities. The directory currently documents 94 distinct prefixes within 331 in detail, a working subset of the prefix population the code carries.

Aurora's median household income runs well above the US figure, in line with the broader west suburban Chicago corridor where corporate offices, professional services, and higher-income residential development have shaped the regional economy. Home values come in close to the national median, the city's median age sits a few years under the US reading, and population places Aurora as one of the larger Illinois cities outside Chicago itself — substantial enough to anchor its own civic identity within the broader metropolitan area.