160,080 people (2024 Census estimate, +4.6% since 2020)
613 square miles of land · 261 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.
75 active community water systems list Johnson County in the area they serve, reporting 184,931 people served in all (a system that crosses county lines counts its whole population).
| IOWA CITY WATER DEPARTMENT surface water · local government · IA5225079 | 68,753 served |
| UNIVERSITY WATER SYSTEM surface water · state · IA5225101 | 47,136 served |
| NORTH LIBERTY WATER SUPPLY groundwater · local government · IA5252072 | 23,276 served |
| CORALVILLE MUNI WATER SYSTEM groundwater · local government · IA5208071 | 22,318 served |
| TIFFIN WATER SUPPLY groundwater · local government · IA5288021 | 7,577 served |
| SOLON WATER DEPT groundwater · local government · IA5282062 | 3,018 served |
| LONE TREE MUNI WATER SYSTEM groundwater · local government · IA5240095 | 1,357 served |
| LAKE RIDGE, INCORPORATED groundwater · private · IA5225315 | 1,300 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 69 people were held in Johnson County's jail, in Vera's latest figure (2021), or 63 per 100,000 residents ages 15–64. In 2016 it was about 92.
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.
4 school districts have their office in Johnson County. School taxes are usually the largest part of a property tax bill.
Spent $274.2 million — $211.6 million to run schools, about $14,290 per student, plus $48.4 million on buildings and equipment. Money in: $125.6 million local (mostly property tax), $115.2 million state, $31.9 million federal. Long-term debt: $233 million.
Spent $49.9 million — $38.5 million to run schools, about $12,575 per student, plus $6.3 million on buildings and equipment. Money in: $30.9 million local (mostly property tax), $23.2 million state, $2.5 million federal. Long-term debt: $102 million.
Spent $20.3 million — $16.6 million to run schools, about $10,891 per student, plus $2.3 million on buildings and equipment. Money in: $12.3 million local (mostly property tax), $11.5 million state, $819,000 federal. Long-term debt: $28.4 million.
Spent $6.4 million — $5.2 million to run schools, about $12,091 per student, plus $811,000 on buildings and equipment. Money in: $3.9 million local (mostly property tax), $2.6 million state, $287,000 federal. Long-term debt: $2.4 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 Moderate compared with other U.S. counties. FEMA estimates natural hazards cost Johnson County about $96.3 million a year on average in buildings, crops and lives. Ability to bounce back (community resilience): Very High; social vulnerability: Very Low.
Source: FEMA National Risk Index (December 2025), expected annual loss. Ratings compare counties nationwide; they're estimates, not predictions.
376 bridges in Johnson County: 156 in good condition, 186 fair, and 34 poor (9.0%). “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.
| GILBERT ST over RALSTON CREEK · built 1972 | 14,025 vehicles a day |
| IA 1 NB over IOWA RIVER · built 1915 | 10,950 vehicles a day |
| IOWA AVE over IOWA RIVER · built 1916 | 5,400 vehicles a day |
| KIRKWOOD AVE over RALSTON CREEK · built 1935 | 4,693 vehicles a day |
| DODGE ST over OVER IAIS RR · built 1970 | 4,688 vehicles a day |
| WASHINGTON ST over RALSTON CREEK · built 1910 | 2,487 vehicles a day |
Source: Federal Highway Administration, National Bridge Inventory (2025 submission). Includes state, county and city bridges.
Federal grants paid for $279.3 million of work in Johnson County in fiscal 2025, about $1,827 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 Iowa 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 Johnson 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 Johnson County built: brayden.ozark@gmail.com.
More of Iowa: the state government and every county in Iowa.
Nearby counties: Iowa County (24 mi) · Washington County (25 mi) · Cedar County (25 mi) · Muscatine County (28 mi) · Linn County (28 mi) · Louisa County (36 mi).