14,260 people (2024 Census estimate, +0.8% since 2020)
573 square miles of land · 25 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.
7 active community water systems list O'Brien County in the area they serve, reporting 11,182 people served in all (a system that crosses county lines counts its whole population).
| SHELDON WATER DEPARTMENT groundwater · local government · IA7170040 | 5,512 served |
| HARTLEY MUNICIPAL WATER DEPARTMENT groundwater · local government · IA7128036 | 1,605 served |
| SANBORN WATER SUPPLY groundwater · local government · IA7165025 | 1,392 served |
| PAULLINA MUNICIPAL WATER SUPPLY groundwater · local government · IA7139032 | 996 served |
| PRIMGHAR MUNICIPAL WATER SUPPLY groundwater · local government · IA7155059 | 902 served |
| SUTHERLAND WATER SUPPLY buys groundwater · local government · IA7177007 | 629 served |
| CALUMET WATER SUPPLY buys groundwater · local government · IA7109065 | 146 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 34 people were held in O'Brien County's jail, in Vera's latest figure (2020), or 414 per 100,000 residents ages 15–64. In 2015 it was about 35.
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 O'Brien County. School taxes are usually the largest part of a property tax bill.
Spent $16.6 million — $14.2 million to run schools, about $11,849 per student, plus $1.9 million on buildings and equipment. Money in: $7.6 million local (mostly property tax), $9.9 million state, $1.5 million federal. Long-term debt: $1.9 million.
Spent $10.7 million — $8.4 million to run schools, about $12,707 per student, plus $821,000 on buildings and equipment. Money in: $7.9 million local (mostly property tax), $4.7 million state, $887,000 federal. Long-term debt: $20.2 million.
Spent $9.8 million — $7.9 million to run schools, about $13,648 per student, plus $1.3 million on buildings and equipment. Money in: $7.3 million local (mostly property tax), $2.8 million state, $671,000 federal.
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 O'Brien County about $11.1 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.
263 bridges in O'Brien County: 128 in good condition, 119 fair, and 16 poor (6.1%). “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.
| FM over WILLOW CREEK · built 1964 | 279 vehicles a day |
| LOCAL over GINGER CREEK · built 1952 | 62 vehicles a day |
| LOCAL over MILL CREEK · built 1924 | 50 vehicles a day |
| LOCAL over GRASS WATERWAY · built 1954 | 50 vehicles a day |
| LOCAL over LAMKIN CREEK · built 1945 | 35 vehicles a day |
| FM over WATERMAN CREEK · built 2003 | 34 vehicles a day |
Source: Federal Highway Administration, National Bridge Inventory (2025 submission). Includes state, county and city bridges.
Federal grants paid for $1 million of work in O'Brien County in fiscal 2025, about $72 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 O'Brien 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 O'Brien County built: brayden.ozark@gmail.com.
More of Iowa: the state government and every county in Iowa.
Nearby counties: Osceola County (20 mi) · Cherokee County (24 mi) · Clay County (24 mi) · Sioux County (28 mi) · Dickinson County (30 mi) · Buena Vista County (34 mi).