15,444 people (2024 Census estimate, −1.5% since 2020)
445 square miles of land · 35 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.
9 active community water systems list Carroll County in the area they serve, reporting 11,162 people served in all (a system that crosses county lines counts its whole population).
| SAVANNA groundwater · local government · IL0150250 | 3,020 served |
| THOMSON MAXIMUM SECURITY CENTER buys groundwater · federal · IL0150030 | 2,166 served |
| LANARK groundwater · local government · IL0150100 | 1,504 served |
| MOUNT CARROLL groundwater · local government · IL0150200 | 1,479 served |
| MILLEDGEVILLE groundwater · local government · IL0150150 | 989 served |
| SHANNON groundwater · local government · IL0150300 | 801 served |
| THOMSON groundwater · local government · IL0150350 | 600 served |
| CHADWICK groundwater · local government · IL0150050 | 523 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 17 people were held in Carroll County's jail, in Vera's latest figure (2019), or 177 per 100,000 residents ages 15–64. In 2014 it was about 20.
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.
3 school districts have their office in Carroll County. School taxes are usually the largest part of a property tax bill.
Spent $17.6 million — $13.8 million to run schools, about $15,375 per student, plus $2.2 million on buildings and equipment. Money in: $9.4 million local (mostly property tax), $9.1 million state, $2.9 million federal. Long-term debt: $6 million.
Spent $17.5 million — $11.7 million to run schools, about $16,420 per student, plus $5 million on buildings and equipment. Money in: $9.2 million local (mostly property tax), $3.9 million state, $1.1 million federal. Long-term debt: $5.6 million.
Spent $7.9 million — $6.6 million to run schools, about $16,145 per student, plus $695,000 on buildings and equipment. Money in: $4.7 million local (mostly property tax), $3.6 million state, $716,000 federal. Long-term debt: $7.2 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: Very Low compared with other U.S. counties. FEMA estimates natural hazards cost Carroll County about $10.8 million a year on average in buildings, crops and lives. Ability to bounce back (community resilience): Relatively High; social vulnerability: Relatively Moderate.
Source: FEMA National Risk Index (December 2025), expected annual loss. Ratings compare counties nationwide; they're estimates, not predictions.
180 bridges in Carroll County: 58 in good condition, 96 fair, and 26 poor (14.4%). “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.
| ARGO FAY ROAD over STREAM · built 1937 | 2,350 vehicles a day |
| E MILLEDGEVILLE RT over ELKHORN CREEK · built 1939 | 1,050 vehicles a day |
| TR-38 (W Wacker Rd over PLUM RIVER · built 1977 | 775 vehicles a day |
| OIL VALLEY SCHOOL over EAST JOHNSON CREEK · built 1980 | 200 vehicles a day |
| OIL VALLEY SCHOOL over JOHNSON CREEK · built 1986 | 200 vehicles a day |
| VANBUSKIRK RD over STRADDLE CREEK · built 1982 | 200 vehicles a day |
Source: Federal Highway Administration, National Bridge Inventory (2025 submission). Includes state, county and city bridges.
Federal grants paid for $18 million of work in Carroll County in fiscal 2025, about $1,149 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 Carroll 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 Carroll County built: brayden.ozark@gmail.com.
More of Illinois: the state government and every county in Illinois.
Nearby counties: Whiteside County (22 mi) · Stephenson County (23 mi) · Jo Daviess County (25 mi) · Ogle County (31 mi) · Clinton County, IA (33 mi) · Jackson County, IA (34 mi).