Population100,420 (2020 Census)
University Energy Grows Beside Historic Town Squares
DeKalb County, IllinoisSycamore serves as the county seat, and DeKalb is home to Northern Illinois University. Agricultural communities surround these two neighboring centers of county life. This guide brings together a starting point for county information, public services and local connections. Begin with Sycamore, then use the resource links to plan the details of a visit or an everyday errand. Check directly with each provider for current hours, access and service availability before setting out.
DeKalb County at a Glance
Population100,420 (2020 Census)
County SeatSycamore
Largest MunicipalityDeKalb
Established1837
ZIP Codes22 ZIP codes wholly or partly within the county (checked October 4, 2026)
Total Area634.6 sq mi (land and water; 2020 Census geography)
Major RoutesInterstate 88; US Route 30; US Route 34; Illinois Route 23; Illinois Route 38
Area Codes331 / 630 / 779 / 815 (common local area codes)
Meet Your County Advertisers
Local Connections for Everyday Needs
Explore Prairie State Water Systems Inc for water well systems.
Discover DeKalb County
DeKalb County
The county was created from Kane County in 1837. It was named for Johann de Kalb, who served in the American Revolutionary War. Today, Sycamore remains the county seat, while DeKalb is its largest municipality. The 2020 Census counted 100,420 residents across the county. Its towns and surrounding countryside offer different ways to understand the same place: through public buildings, transportation routes and the communities that connect them. Local records and historical collections provide a starting point for exploring how those connections changed over time.
Life in DeKalb County extends beyond a single town center. University and agricultural connections are part of the local setting, alongside the routine needs of households, schools and businesses. Use county offices for the services they administer and contact municipal or township offices when a question concerns a specific address. Planning around the actual destination helps make visits, appointments and local errands more practical, especially when travel crosses town or county boundaries.
What Shapes Us
Local Heritage
Established in 1837, DeKalb County has a history recorded in its communities and public institutions. Start with local collections to explore specific people, buildings and events.
Landscape and Connections
University and agricultural connections help distinguish DeKalb County. Its county seat, Sycamore, provides a useful starting point for understanding how nearby communities connect across the area.
Everyday Community
County and local offices connect residents with practical services. Follow the linked providers for details specific to your destination, address and purpose in DeKalb County.
Explore the towns, follow the stories, make local connections.
A Look Around
Scenes from DeKalb County
Places and details that tell a local story.
Shaw Local
DeKalb County property transfers: Oct. 5 to 11
Read the full story at Shaw Local.
Read the Story Oct 18, 2026 • Local news
Around DeKalb County
Stories from every corner of DeKalb County.
DeKalb County property transfers: Oct. 5 to 11
Read the full story at Shaw Local.
Oct 18, 2026 • Local news
These residential properties were the best deals for DeKalb County's in the week of Oct. 5
Read the full story at Shaw Local.
Oct 17, 2026 • Local news
Your guide to the November 2026 election in DeKalb County
Read the full story at Shaw Local.
Oct 17, 2026 • Local news
What $300,000 can buy you in DeKalb County, Oct. 5-11
Read the full story at Shaw Local.
Oct 16, 2026 • Local news
Keep These Businesses in Mind
Start with a Direct Conversation
Contact Prairie State Water Systems Inc directly to ask about current options, availability and the services you need.
County Resources
Find the Right Local Connection
Start with the responsible public agency or service provider. Statewide links are labeled so you can locate the office that serves your address.
Government
County & Local Resources
Supervisor of Assessments
Property assessments, exemptions and assessment office information.
Phone (815) 895-7120
Schools
County & Local Resources
Hospitals and Health
County & Local Resources
Northwestern Medicine Kishwaukee Hospital
ONE KISH HOSPITAL DRIVE, Dekalb; (815) 756-1521.
Phone (815) 756-1521
Advocate Sherman Hospital
Regional option in Kane County
Address 1425 NORTH RANDALL ROAD, Elgin
Phone (847) 742-9800
Copley Memorial Hospital
Regional option in Kane County
Address 2000 OGDEN AVENUE, Aurora
Phone (630) 978-6200
Northwestern Medicine Delnor Community Hospital
Regional option in Kane County
Address 300 RANDALL RD, Geneva
Phone (630) 208-3000
Public Safety
County & Local Resources
Illinois State Police
Statewide or federal resource; select the office or service for your address.
Illinois State Police contacts
Find the appropriate State Police contact; call 911 for emergencies.
FBI Internet Crime Complaint Center
Report cyber-enabled crime through the federal complaint portal; emergencies require 911.
Emergency Services
County & Local Resources
Illinois Emergency Management Agency and Office of Homeland Security
Statewide or federal resource; select the office or service for your address.
National Weather Service
Statewide or federal resource; select the office or service for your address.
State Parks
County & Local Resources
Chain O'Lakes State Park
Spring Grove — regional option in McHenry County. Check facilities and access notices.
Moraine Hills State Park
McHenry — regional option in McHenry County. Check facilities and access notices.
Matthiessen State Park
Utica — regional option in LaSalle County. Check facilities and access notices.
Buffalo Rock State Park
Ottawa — regional option in LaSalle County. Check facilities and access notices.
William W. Powers Conservation Area
Chicago — regional option in Cook County. Check facilities and access notices.
Trails
County & Local Resources
Fox River Bike Trail & Fabyan Forest Preserve
Geneva — regional option in Kane County. Check trail access and permitted uses.
Fox River Trail
St. Charles — regional option in Kane County. Check trail access and permitted uses.
Hawthorne Hill Nature Center
Elgin — regional option in Kane County. Check trail access and permitted uses.
Johnson's Mound Forest Preserve
Elburn — regional option in Kane County. Check trail access and permitted uses.
Kuipers Family Farm
Maple Park — regional option in Kane County. Check trail access and permitted uses.
Utilities
County & Local Resources
Illinois Commerce Commission
Statewide or federal resource; select the office or service for your address.
Illinois 811 — JULIE
Statewide or federal resource; select the office or service for your address.
Illinois energy assistance
Find utility-bill assistance and the local administering agency.
Libraries
County & Local Resources
Clinton Township Public Library
Address 110 South Elm Street Post Office Box 299 Waterman , IL 60556-0299
Phone 815-264-3339
Cortland Community Library
Address 63 South Somonauk Road Post Office Box 486 Cortland , IL 60112-0486
Phone 815-756-7274
Flewellin Memorial Library
Address 108 West Comanche Avenue Post Office Box 190 Shabbona , IL 60550-0190
Phone 815-824-2079
Courts
County & Local Resources
Illinois Courts
Statewide or federal resource; select the office or service for your address.
Illinois Courts — Forms
Statewide or federal resource; select the office or service for your address.
Illinois Court Help
Court-process information and help for people without an attorney.
DMV
County & Local Resources
Transportation
County & Local Resources
Illinois Department of Transportation
Statewide or federal resource; select the office or service for your address.
Getting Around Illinois
Statewide or federal resource; select the office or service for your address.
Illinois public transportation
Find public transportation information and regional agencies.
IDOT transit programs
Transit program information, including rural and intercity services.
Amtrak Illinois services
Find Illinois intercity rail routes and stations; some counties require travel to a regional station.
Postal Services
County & Local Resources
USPS Location Finder
Statewide or federal resource; select the office or service for your address.
USPS ZIP Code Lookup
Statewide or federal resource; select the office or service for your address.
USPS Informed Delivery
Statewide or federal resource; select the office or service for your address.
Veterans
County & Local Resources
Illinois Department of Veterans Affairs
Statewide or federal resource; select the office or service for your address.
VA Facility Locator
Statewide or federal resource; select the office or service for your address.
Veterans Crisis Line
Statewide or federal resource; select the office or service for your address.
Employment
County & Local Resources
IllinoisJobLink — official job-seeker help
Statewide or federal resource; select the office or service for your address.
Illinois Department of Employment Security
Statewide or federal resource; select the office or service for your address.
Illinois workNet
Statewide or federal resource; select the office or service for your address.
Work for Illinois
Statewide or federal resource; select the office or service for your address.
A Useful Starting Point
County facts and practical links for everyday questions.
Questions and Answers
Get to Know DeKalb County
Find background and service information below, then follow the provider links for current details.
Sycamore is the county seat. Confirm the specific office and its current location before traveling.
DeKalb is the largest municipality listed in the county reference. Countywide statistics include other communities and unincorporated areas as well.
The 2020 Census counted 100,420 residents. This is a decennial count, not a current-year population estimate.
DeKalb County was established in 1837. The county was created from Kane County in 1837. It was named for Johann de Kalb, who served in the American Revolutionary War.
The county covers approximately 634.6 sq mi (land and water; 2020 Census geography). This total includes both land and water, rather than land area alone.
Sycamore serves as the county seat, and DeKalb is home to Northern Illinois University. Agricultural communities surround these two neighboring centers of county life.
Kuipers Family Farm is in Maple Park, Kane County. This is a regional option outside DeKalb County. Check the provider’s current opening times and visitor information before traveling.
Use USPS ZIP Code Lookup with the full street address. A county boundary does not define a single postal delivery area.
Kuipers Family Farm is in Maple Park, Kane County. This is a regional option outside DeKalb County. Check the provider’s current opening times and visitor information before traveling.
Matthiessen State Park is in Utica, LaSalle County. This is a regional option outside DeKalb County. Basic access is the free activity; extras may carry charges. Check the provider’s current opening times and visitor information before traveling.
Begin with the Illinois Department of Veterans Affairs to locate the appropriate service office, or the VA facility locator for federal facilities.
Meet Your County Advertisers
Local Connections for Everyday Needs
Explore Prairie State Water Systems Inc for water well systems.
My Local Guide
Find Something Fun
Explore Local PlacesPlan your next stop around current information from each place.
Kids’ Fun
- Kuipers Family Farm — Maple Park — regional option in Kane County
- Woody's Orchard — Plano — regional option in Kendall County
- Sugar Grove Family Fun Center — Sugar Grove — regional option in Kane County
Restaurants
- Fatty's Pub & Grille — DeKalb, DeKalb County
- Pizza Villa — DeKalb, DeKalb County
- Rosita's Mexican Restaurant — DeKalb, DeKalb County
Shopping & Retail
- Cracker Jax — DeKalb, DeKalb County
- Urban Grace — DeKalb, DeKalb County
- Inboden's Meat Market and Full Service Catering — DeKalb, DeKalb County
Clothing & Boutiques
- Cracker Jax — DeKalb, DeKalb County
- Urban Grace — DeKalb, DeKalb County
- The Rustic Fox — North Aurora — regional option in Kane County
Outdoor Fun
- Kuipers Family Farm — Maple Park — regional option in Kane County
- Rochelle Railroad Park — Rochelle — regional option in Ogle County
- Johnson's Mound Forest Preserve — Elburn — regional option in Kane County
Free Things To Do
- Matthiessen State Park — Utica — regional option in LaSalle County; basic grounds/trail visit. Rentals, camping, special activities or events may cost extra.
- Buffalo Rock State Park — Ottawa — regional option in LaSalle County; basic grounds/trail visit. Rentals, camping, special activities or events may cost extra.
- Moraine Hills State Park — McHenry — regional option in McHenry County; basic grounds/trail visit. Rentals, camping, special activities or events may cost extra.
Make Time for Local DiscoveriesChoose Your Next Stop