101,335 people (2024 Census estimate, +1.0% since 2020)
631 square miles of land · 161 people per square mile
“Highest” and “lowest” are just order, not grades: a high rank for poverty or hazard losses means more of it. Each figure's source is in its section below.
20 active community water systems list DeKalb County in the area they serve, reporting 94,140 people served in all (a system that crosses county lines counts its whole population).
| DEKALB groundwater · local government · IL0370100 | 40,290 served |
| SYCAMORE groundwater · local government · IL0370550 | 18,500 served |
| SANDWICH groundwater · local government · IL0374850 | 7,156 served |
| NORTHERN ILLINOIS UNIVERSITY-DEKALB buys groundwater · state · IL0375500 | 6,500 served |
| GENOA groundwater · local government · IL0370150 | 5,298 served |
| CORTLAND groundwater · local government · IL0370051 | 4,398 served |
| HINCKLEY groundwater · local government · IL0370200 | 2,006 served |
| SOMONAUK groundwater · local government · IL0374870 | 1,860 served |
Source: U.S. EPA Safe Drinking Water Information System (SDWIS), active community systems, . Look up any system's violations and test results with EPA's search using its ID.
About 122 people were held in DeKalb County's jail, in Vera's latest figure (2023), or 179 per 100,000 residents ages 15–64. In 2018 it was about 123.
Source: Vera Institute of Justice, Incarceration Trends (built from federal Bureau of Justice Statistics jail surveys). Counties without their own jail, or that share one, may show no figure.
8 school districts have their office in DeKalb County. School taxes are usually the largest part of a property tax bill.
Spent $149.9 million — $127.7 million to run schools, about $18,665 per student, plus $9.3 million on buildings and equipment. Money in: $65.4 million local (mostly property tax), $80.7 million state, $18.7 million federal. Long-term debt: $85.9 million.
Spent $79.6 million — $64.4 million to run schools, about $17,897 per student, plus $9.5 million on buildings and equipment. Money in: $44.5 million local (mostly property tax), $30.4 million state, $2 million federal. Long-term debt: $83.8 million.
Spent $29.7 million — $29 million to run schools, about $15,319 per student, plus $136,000 on buildings and equipment. Money in: $18.1 million local (mostly property tax), $11 million state, $2.8 million federal. Long-term debt: $3.3 million.
Spent $30.2 million — $25.3 million to run schools, about $16,416 per student, plus $2.6 million on buildings and equipment. Money in: $13.9 million local (mostly property tax), $15 million state, $2.8 million federal. Long-term debt: $9.5 million.
Spent $13.9 million — $13.1 million to run schools, about $17,405 per student, plus $351,000 on buildings and equipment. Money in: $10.1 million local (mostly property tax), $5.6 million state, $928,000 federal. Long-term debt: $6.5 million.
Spent $15.4 million — $12.8 million to run schools, about $17,994 per student, plus $2.4 million on buildings and equipment. Money in: $11.4 million local (mostly property tax), $5.5 million state, $944,000 federal. Long-term debt: $750,000.
Spent $14.3 million — $13.7 million to run schools, about $19,730 per student, plus $274,000 on buildings and equipment. Money in: $10.7 million local (mostly property tax), $4.8 million state, $911,000 federal. Long-term debt: $4.2 million.
Spent $8.3 million — $7.4 million to run schools, about $17,612 per student, plus $405,000 on buildings and equipment. Money in: $5.9 million local (mostly property tax), $4 million state, $1.2 million federal. Long-term debt: $4.2 million.
Source: U.S. Census Bureau, 2023 Annual Survey of School System Finances. Districts are listed by the county of their main office; some serve neighboring counties too.
Source: County Health Rankings & Roadmaps 2025 (University of Wisconsin Population Health Institute), which gathers federal data (CDC, Census, and others); measures cover different recent years. Blank lines aren't reported for small counties.
Overall risk: Relatively Low compared with other U.S. counties. FEMA estimates natural hazards cost DeKalb County about $47.4 million a year on average in buildings, crops and lives. Ability to bounce back (community resilience): Relatively High; social vulnerability: Relatively Low.
Source: FEMA National Risk Index (December 2025), expected annual loss. Ratings compare counties nationwide; they're estimates, not predictions.
262 bridges in DeKalb County: 103 in good condition, 126 fair, and 33 poor (12.6%). “Poor” means a main part — the deck, the beams, or the supports — is rated 4 or lower on the federal 0–9 scale. It doesn't mean unsafe to drive; unsafe bridges are closed.
| Annie Glidden Rd. over Watson Creek · built 1971 | 13,600 vehicles a day |
| IL 64 FAP 17 over DRAINAGE DITCH · built 1937 | 4,500 vehicles a day |
| IL 23 over DEER CREEK TRIB. · built 1987 | 3,600 vehicles a day |
| GLIDDEN RD over LEE SLOUGH CREEK · built 1997 | 3,550 vehicles a day |
| FAS-96 (Somonauk R over Buck Br Somonauk Cr · built 1996 | 3,250 vehicles a day |
| GLIDDEN RD over LEE SLOUGH CREEK · built 1997 | 3,150 vehicles a day |
Source: Federal Highway Administration, National Bridge Inventory (2025 submission). Includes state, county and city bridges.
Federal grants paid for $34.6 million of work in DeKalb County in fiscal 2025, about $345 per resident — to the county, cities, schools, hospitals, nonprofits and others.
Source: USAspending.gov, grants by place of performance, fiscal 2025 (Oct. 2024 to Sept. 2025). Search it by county to see each award.
From Grants.gov: posted grants listing county governments as eligible, soonest deadline first; research-only and overseas programs left out; list updated 2026-10-13, refreshed weekly. 62 are open in all. Cities, towns, school districts and nonprofits have their own lists there.
Registration deadlines, early voting and polling places for Illinois are on the federal site vote.gov, which links to the state's official election office.
The budget, property tax rates, audits, local officials and offices for DeKalb County come from the county's own records, which we haven't gathered — not gathered, never hidden. See what a full county site looks like, or ask to have DeKalb County built: brayden.ozark@gmail.com.
More of Illinois: the state government and every county in Illinois.
Nearby counties: Kane County (18 mi) · Kendall County (27 mi) · Lee County (29 mi) · Boone County (29 mi) · Ogle County (30 mi) · McHenry County (34 mi).