DeKalb County, Illinois
County seat: Sycamore · Population 101,835 (2025) · 631 sq mi
DeKalb County is the 19th most populous of Illinois's 102 counties, with 101,835 people (2025 estimate). Its county seat is Sycamore. It is part of the Northeast region, one of the 10 Illinois economic development regions (DCEO). The map shows its 14 cities and towns and the 8 neighboring counties.
DeKalb County facts
- County seat
- Sycamore
- Population (2025 estimate)
- 101,835 +1.3% since 2020
- Land area
- 631 sq mi 30th largest of 102
- Water area
- 3 sq mi
- Population density
- 161 per sq mi
- Established
- 1837
- Same name
- One of 6 DeKalb Counties in the US
- Named after
- Johann de Kalb American general (1721-1780)
- Largest city
- DeKalb 40,467
- Median household income
- $70,724
- Cities and towns
- 14
- ZIP codes
- 22
- Time zone
- Central
- FIPS code
- 17037
Cities and towns in DeKalb County
DeKalb County has 14 incorporated cities, towns and villages. Populations count the people living inside DeKalb County; cities that cross a county line also list the other counties.
| Name | Type | Population 2025 | Also in |
|---|---|---|---|
| DeKalb | City | 40,467 | |
| Sycamore (county seat) | City | 19,083 | |
| Sandwich | City | 7,209 | Kendall County |
| Genoa | City | 5,547 | |
| Cortland | Town | 4,676 | |
| Hinckley | Village | 1,996 | |
| Waterman | Village | 1,640 | |
| Kirkland | Village | 1,632 | |
| Somonauk | Village | 1,539 | LaSalle County |
| Malta | Village | 1,140 | |
| Kingston | Village | 1,103 | |
| Shabbona | Village | 867 | |
| Maple Park | Village | 761 | Kane County |
| Lee | Village | 122 | Lee County |
ZIP codes in DeKalb County
22 ZIP codes reach into DeKalb County. ZIP codes ignore county lines, so some also cover a neighboring county.
- 60111
- 60112
- 60115
- 60129 also Ogle County
- 60135 also McHenry and Boone counties
- 60140 also Kane and McHenry counties
- 60145 also Boone County
- 60146 also Boone and Ogle counties
- 60150
- 60151 also Kane County
- 60152 also McHenry County
- 60178 also Kane County
- 60511 also Kane County
- 60518 also LaSalle and Lee counties
- 60520
- 60530 also Lee County
- 60531 also LaSalle County
- 60548 also LaSalle and Kendall counties
- 60550
- 60552 also LaSalle County
- 60556
- 61068 also Ogle and Lee counties
Population of DeKalb County, 2020–2025
DeKalb County grew by 1,313 people (+1.3%) between April 2020 and July 2025: 811 more births than deaths and a net gain of 347 people from migration.
| Year (July 1) | Population |
|---|---|
| 2020 | 100,366 |
| 2021 | 101,100 |
| 2022 | 100,185 |
| 2023 | 100,131 |
| 2024 | 100,621 |
| 2025 | 101,835 |
Neighboring counties
- Kane County east · 525,757 people
- Lee County west · 32,914 people
- Ogle County west · 51,399 people
- LaSalle County south · 107,773 people
- Boone County north · 53,568 people
- Kendall County southeast · 145,470 people
- McHenry County northeast · 317,751 people
- Winnebago County northwest · 283,674 people
Printable DeKalb County map
The PDF is a vector file with real text: it prints sharp on Letter paper and you can search it for a town. The PNG is 2400 pixels wide for slides and documents. Both are free to use with a credit to WhichCounty.
- PDF (Letter) (107 KB)
- PNG (2400 px) (77 KB)
Paste this code to embed the map on your site:
Sources
- Boundaries: U.S. Census Bureau, 2025 Cartographic Boundary Files (1:500,000).
- Population: Census Bureau county and city estimates, Vintage 2025. CDP populations: American Community Survey 2020–2024.
- Places and ZIP codes: Census Bureau 2026 Gazetteer and 2020 ZIP Code Tabulation Area relationship files.
- County seat, founding year and name origin: Wikidata (CC0), checked against state sources.
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