Area Code 815 Location

Area code 815 serves a broad stretch of northern Illinois, including the city of Joliet on the southwest edge of the Chicago metro. Established in 1947, it covers communities along the Rock, Fox, and Illinois Rivers and remains one of the state’s most recognizable telephone prefixes. In 2007, the 779 overlay was added, so ten-digit dialing is standard for local calls across the 815/779 region. If you spot an 815 phone number, it typically points to northern Illinois locations outside the core Chicago area.

Major cities and towns covered by area code 815 include:

• Joliet
• Rockford
• DeKalb
• Kankakee
• Crystal Lake
• McHenry
• Woodstock
• Belvidere
• Ottawa
• LaSalle–Peru
• Sterling
• Dixon
• Freeport
• Morris

In Joliet, IL, 815 (with the 779 overlay) supports a fast-growing hub known for the Rialto Square Theatre, the Old Joliet Prison, and historic Route 66. The Illinois & Michigan Canal runs through the city, linking Joliet’s past in transportation and industry to today’s neighborhoods and businesses. Because of the overlay, new phone numbers in the region can be assigned with 779 while many established lines remain 815. The code also connects university towns like DeKalb, factory centers, and rural communities, tying together a wide mix of northern Illinois life.

Area code 815 was one of the original North American Numbering Plan codes created in 1947, and the western portion later split off as area code 309 in 1957. Today, the 815/779 complex serves much of northern Illinois outside Chicago, including the Rockford area and cities along the state line with Wisconsin. Local calls require 10 digits due to the overlay, while long-distance dialing follows standard U.S. formats. For callers and businesses, 815 remains a trusted signal of northern Illinois roots.

Statistic: Established 1947; overlay 779 added in 2007 — Source: North American Numbering Plan Administration (NANPA)