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  5. Area Code 815

Where Is Area Code 815?

Area code 815 is found in the US state of Illinois. Primarily servicing the city of Rockford (population: 187116), area code 815 covers 24 counties of Illinois.

Located in the Central time zone, area code 815 is on the same time as Chicago, IL.

Area code 815 was brought into effect on January 1, 1947.

Map of  with area code 815 highlighted

Counties in Area Code 815

  • Boone,
  • Bureau,
  • Carroll,
  • DeKalb,
  • Ford,
  • Grundy,
  • Iroquois,
  • Jo Daviess,
  • Kane,
  • Kankakee,
  • Kendall,
  • La Salle,
  • Lee,
  • Livingston,
  • Marshall,
  • McHenry,
  • McLean,
  • Ogle,
  • Putnam,
  • Stephenson,
  • Whiteside,
  • Will,
  • Winnebago.

Most Populous Cities in Area Code 815

City County City Population Time Zone
Rockford Winnebago 187,116 CST
Plainfield Will 95,378 CST
Crystal Lake McHenry 59,550 CST
McHenry McHenry 56,699 CST
DeKalb DeKalb 46,071 CST
Romeoville Will 40,098 CST
Lockport Will 37,138 CST
Kankakee Kankakee 37,023 CST
New Lenox Will 34,312 CST
Belvidere Boone 34,167 CST
Woodstock McHenry 32,163 CST
Freeport Stephenson 31,152 CST
Frankfort Will 30,645 CST
Bourbonnais Kankakee 29,002 CST
Ottawa La Salle 24,043 CST
Loves Park Winnebago 23,248 CST
Dixon Lee 23,113 CST
Machesney Park Winnebago 22,929 CST
Homer Glen Will 22,909 CST
Sycamore DeKalb 21,749 CST
Sterling Whiteside 21,680 CST
Morris Grundy 20,421 CST
Streator La Salle 19,966 CST
Roscoe Winnebago 19,835 CST
Rochelle Ogle 14,676 CST

Note: The above list is based off of the top 25 most populous cities in the area code as per 2012 United States Census Bureau estimates.

View all United States Area Codes.

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This page was last updated on July 3, 2015.