38,478 people (2024 Census estimate, +7.7% since 2020)
429 square miles of land · 90 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.
18 active community water systems list Warren County in the area they serve, reporting 23,595 people served in all (a system that crosses county lines counts its whole population).
| WARRENTON PWS groundwater · local government · MO6010834 | 8,208 served |
| MONTGOMERY CO PWSD 1 groundwater · local government · MO6024406 | 3,850 served |
| ST CHARLES CO PWSD #2 WRIGHT CITY groundwater · local government · MO6010874 | 3,550 served |
| MARTHASVILLE PWS groundwater · local government · MO6010505 | 1,200 served |
| MO AMERICAN WARREN COUNTY WATER & SEWER groundwater · private · MO6036149 | 1,200 served |
| ST CHARLES COUNTY PWSD 2 WARREN groundwater · local government · MO6024629 | 1,192 served |
| LAKE SHERWOOD SUBD groundwater · private · MO6036039 | 1,100 served |
| TRUESDALE PWS groundwater · local government · MO6010799 | 853 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 91 people were held in Warren County's jail, in Vera's latest figure (2019), or 414 per 100,000 residents ages 15–64. In 2014 it was about 100.
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.
2 school districts have their office in Warren County. School taxes are usually the largest part of a property tax bill.
Spent $39.4 million — $35.8 million to run schools, about $11,611 per student, plus $2.6 million on buildings and equipment. Money in: $18.4 million local (mostly property tax), $20.7 million state, $5.1 million federal. Long-term debt: $15.7 million.
Spent $34.3 million — $22.8 million to run schools, about $12,881 per student, plus $9.5 million on buildings and equipment. Money in: $17.8 million local (mostly property tax), $12.1 million state, $4.3 million federal. Long-term debt: $40.2 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 Warren County about $27.3 million a year on average in buildings, crops and lives. Ability to bounce back (community resilience): Relatively High; social vulnerability: Very Low.
Source: FEMA National Risk Index (December 2025), expected annual loss. Ratings compare counties nationwide; they're estimates, not predictions.
151 bridges in Warren County: 46 in good condition, 96 fair, and 9 poor (6.0%). “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.
| RT D E over TUQUE & WOLF CR · built 1958 | 1,836 vehicles a day |
| RT A S over IS 70 · built 1961 | 1,003 vehicles a day |
| MO 94 E over MASSES CR · built 1953 | 971 vehicles a day |
| MO 94 E over LOUTRE SLU · built 1953 | 971 vehicles a day |
| S STRINGTOWN RD over SMITH BRANCH CR · built 1960 | 300 vehicles a day |
| GODT RD over TRIB OF INDIAN CAM · built 1936 | 150 vehicles a day |
Source: Federal Highway Administration, National Bridge Inventory (2025 submission). Includes state, county and city bridges.
Federal grants paid for $22.9 million of work in Warren County in fiscal 2025, about $645 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 Missouri 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 Warren 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 Warren County built: brayden.ozark@gmail.com.
More of Missouri: the state government and every county in Missouri.
Nearby counties: Montgomery County (20 mi) · Lincoln County (23 mi) · Franklin County (25 mi) · St. Charles County (26 mi) · Gasconade County (29 mi) · Calhoun County, IL (38 mi).