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815
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  3. Area code 815
Illinois (IL)Central Time (CT)

Area Code 815

Illinois (IL) * Rockford, Joliet, Plainfield, Crystal Lake, Mchenry, Amboy, Ancona, Apple River * Central Time (CT)

1.7M

Population

263

ZIP codes

Illinois

Primary state

Central Time (CT)

Time zones

What stands out

  • Coverage: 1.7M people across 263 ZIP codes.
  • Overlapping area codes: 779
  • Major cities: Rockford, Joliet, Plainfield.
Primary state:Illinois (IL)/Major cities:Rockford, Joliet, Plainfield, Crystal Lake, Mchenry, Amboy, Ancona, Apple River

Browse sections

Basics

Percentiles compare this area code to other area codes nationwide.

Population

1.7M

ZIP codes

263

Median age

39.9 yrs

Population density

145.4/sq mi

Mean commute time

27 min

Avg. household size

2.6

Neighbors

Neighboring area codes

217219224262309331447464563608630708
Notes & Sources
  • Area-code boundaries can change over time; verify official assignments with NANPA for critical use.
  • In regions with overlapping area codes, new numbers may use a different code.
  • This page aggregates ZIP-based crosswalks for orientation and does not indicate phone-number availability.

Data freshness

ACS 5-year
2020–2024
Page updated
2026-02-23

Release schedule and upstream dates: Sources.

Data sources

U.S. Census (ACS 5-year)U.S. Census TIGER/LineNANPA

Derived statistics

  • Area codes are not Census geographies; statistics are estimated by aggregating ZCTA (ZIP) values for associated ZIPs.
  • ZIP↔area code associations are derived from NPA boundary polygons and ZCTA centroid points, and can be approximate.
  • Median age, mean commute, and household size are population-weighted; population density uses summed ZIP land area.
Area code overlays and service areas are primarily governed by NANPA; this page uses aggregated geographic overlays for orientation only.

Data accuracy & methodology

This report aggregates 2020–2024 ACS 5-year estimates and geographic overlays for orientation. Area code service areas can cross ZIP/state boundaries and change over time; verify official assignments with NANPA for critical use.