DeKalb County, Illinois

DeKalb County is a county in Illinois, United States, about 65 miles west of Chicago. It had a
population of 100,420 at the 2020 census, an estimated 101,835 by 2025, and covers 635 square
miles (1,640 km2) centred near 41°53′N 88°46′W.

Sycamore is the county seat; its postal code is 60178. The county holds 4 cities, 1 town and 9
villages across 19 townships, and it runs on Central Time. Its FIPS code is 17037.

Towns & Villages in DeKalb County

DeKalb County has 30 named places on record: 4 cities, 1 town, 9 incorporated villages and 16
unincorporated communities with no local government of their own. CDP stands for census
designated place; Unincorp. covers crossroads, rural hamlets and mobile-home parks with no formal
boundary.

Three places on this list straddle county lines. Lee sits on the DeKalb—Lee County line,
with its main street, Viking Vie, following the county boundary itself. Maple Park splits between
DeKalb and Kane counties — most of its land is on the DeKalb side, but most of its 1,433
residents live across the line in Kane County. Somonauk splits the other way: about 92 percent of
its residents live in DeKalb County, with a small share across the line in LaSalle County. Sandwich
also reaches into Kendall County, though its 7,221 residents are overwhelmingly counted in DeKalb.

Townships

DeKalb County has 19 civil townships. The table below lists the townships that anchor an
incorporated place above; the remaining townships (Clinton, Mayfield, Milan, Pierce, South Grove
where unlisted, and Squaw Grove where unlisted) are rural and contain no incorporated place of
their own.

ZIP Codes

• 60115 — DeKalb (also serves the Northern Illinois University campus)
• 60178 — Sycamore
• 60548 — Sandwich
• 60135 — Genoa
• 60112 — Cortland
• 60552 — Somonauk
• 60146 — Kirkland
• 60151 — Maple Park
• 60556 — Waterman
• 60150 — Malta
• 60145 — Kingston
• 60520 — Hinckley
• 60550 — Shabbona
• 60530 — Lee

Fairdale, Esmond, Shabbona Grove, Charter Grove, Clare, Afton Center, Colvin Park, Elva, Five
Points, Franks, McGirr, New Lebanon, Rollo, Wilkinson and the two mobile-home parks have no ZIP
code of their own; mail there is delivered under the nearest incorporated town’s code.

Geography

DeKalb County sits in Illinois’ north-central till plains, a flat expanse of glacial soil
built by the Wisconsin glaciation. Of its 635 square miles, about 631 are land and roughly 3.4 are
water — under one percent, since the county has no large natural lake. The South Branch of
the Kishwaukee River runs through DeKalb and Sycamore, and Shabbona Lake, an artificial reservoir
in Shabbona Township, is the county’s biggest body of water and anchors Shabbona Lake State
Park.

Winnebago County lies to the north, Boone County to the northeast, McHenry County to the east,
Kane County to the southeast, Kendall County to the south-southeast, LaSalle County to the south,
Lee County to the southwest, and Ogle County to the west. Of these eight neighbors, live pages
exist for four: Kane County, LaSalle County, Ogle County and Winnebago County. Boone, McHenry,
Kendall and Lee counties have no matching Illinois page on this site yet.

Demographics

DeKalb County had a population of 100,420 at the 2020 census, and the latest estimate puts the
county near 101,835 residents. DeKalb and Sycamore are by far the two largest communities, with
DeKalb alone holding roughly 40 percent of the county’s population. Median household income
runs about $70,724 (2024 estimate), below Illinois’ statewide figure of $80,306 (2023 ACS).
Population density works out to about 159 people per square mile of land. The county has been a
Democratic stronghold in presidential elections since 2008, a pattern common to counties anchored
by a large public university.

Economy & Local Life

Health care and social assistance employs the most workers in the county, about 7,011 people,
followed by educational services at 6,637 and manufacturing at 6,196. Northern Illinois University
in DeKalb, with roughly 20,000 students, is the county’s largest single employer and the
third-largest university campus in Illinois. Northwestern Medicine operates a hospital in DeKalb,
and large distribution and manufacturing operations for Target, 3M, Nestlé and Ferrara Candy
Company run warehouses in the city. Kishwaukee College, a community college founded in 1968, sits
a mile west of Malta and serves the county alongside NIU. Agriculture remains central outside the
DeKalb-Sycamore core — the county ranks as the second-largest hog-producing county in
Illinois and is credited as the birthplace of the Farm Bureau movement. The Sandwich Fair, founded
in 1858 as a DeKalb County livestock show, is among the oldest continuously running county fairs
in Illinois and can draw crowds over 200,000 on its busiest day each September. Sycamore holds its
own Pumpkin Festival every October, established in 1962.

History

The Illinois General Assembly formed DeKalb County on 4 March 1837, carving it out of Kane
County. It was named for Johann de Kalb, a Bavarian-born officer who served as a major general in
the Continental Army during the American Revolutionary War and died of wounds at the Battle of
Camden in 1780. Sycamore was named for the sycamore trees along the Kishwaukee River and became
the county seat soon after the county’s formation.

DeKalb’s biggest contribution to American agriculture came in 1874, when local farmer
Joseph Glidden patented the modern double-strand barbed wire design in the city, work that helped
fence the open range across the West. DeKalb later became a center for hybrid corn development
starting in 1934, under the DeKalb Agricultural Association, whose winged-ear-of-corn logo became
a familiar sight on Midwestern farms.

Getting There

Interstate 88 crosses the county’s southern half through Sycamore. US Route 30 and US
Route 34 both run through the county, along with several Illinois state highways connecting DeKalb,
Sycamore, Genoa and Sandwich.

• Rockford — about 30 miles northwest
• Chicago — about 65 miles east
• Aurora — about 25 miles southeast
• Rochelle — about 15 miles southwest

Chicago Rockford International Airport, about 30 miles northwest of Sycamore, and O’Hare
International Airport, about 65 miles east, are the nearest major commercial airports. DeKalb
Taylor Municipal Airport handles general aviation. Amtrak does not serve DeKalb County directly;
the nearest station is in Mendota, in neighboring LaSalle County.

Frequently Asked Questions

Where is DeKalb County located?
It sits in north-central Illinois, about 65 miles west of Chicago, bordered by Winnebago, Boone,
McHenry, Kane, Kendall, LaSalle, Lee and Ogle counties.

What is the population of DeKalb County?
100,420 at the 2020 census, with a 2025 estimate near 101,835.

How big is DeKalb County?
635 square miles (1,640 km2), of which about 631 square miles are land.

What is the county seat of DeKalb County?
Sycamore is the county seat; DeKalb, home to Northern Illinois University, is the largest city.

How many towns and villages are in DeKalb County?
Four cities — DeKalb, Sycamore, Sandwich and Genoa — one town (Cortland), nine
incorporated villages, and 16 unincorporated communities and mobile-home parks.

What ZIP codes does DeKalb County use?
60115 for DeKalb, 60178 for Sycamore, 60548 for Sandwich, 60135 for Genoa, and separate codes for
each of the county’s villages, listed above.

What is DeKalb County known for?
Joseph Glidden’s 1874 barbed-wire patent, Northern Illinois University, and being the
birthplace of the Farm Bureau movement.

More counties in this state: Towns and villages in Illinois.