992,929 people (2024 Census estimate, −1.0% since 2020)
508 square miles of land · 1,955 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.
6 active community water systems list St. Louis County in the area they serve, reporting 1,146,683 people served in all (a system that crosses county lines counts its whole population).
| MO AMERICAN ST LOUIS ST CHARLES COUNTIES surface water · private · MO6010716 | 1,111,000 served |
| KIRKWOOD PWS buys surface water · local government · MO6010430 | 28,000 served |
| PACIFIC PWS groundwater · local government · MO6010620 | 6,000 served |
| MO EASTERN CORRECTIONAL CENTER groundwater · state · MO6069017 | 1,100 served |
| MO AMERICAN PEVELY FARMS groundwater · private · MO6031185 | 343 served |
| TERRISAN buys surface water · private · MO6041644 | 240 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 1,138 people were held in St. Louis County's jail, in Vera's latest figure (2024), or 184 per 100,000 residents ages 15–64. In 2019 it was about 1,002.
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.
23 school districts have their office in St. Louis County. School taxes are usually the largest part of a property tax bill.
Spent $293.9 million — $257.6 million to run schools, about $12,527 per student, plus $13.8 million on buildings and equipment. Money in: $249.3 million local (mostly property tax), $72.7 million state, $9.5 million federal. Long-term debt: $147.9 million.
Spent $293.7 million — $239.6 million to run schools, about $13,983 per student, plus $41.3 million on buildings and equipment. Money in: $272.3 million local (mostly property tax), $36.4 million state, $9.9 million federal. Long-term debt: $228 million.
Spent $255.2 million — $225.2 million to run schools, about $13,977 per student, plus $19.5 million on buildings and equipment. Money in: $164.5 million local (mostly property tax), $86.8 million state, $22 million federal. Long-term debt: $164.1 million.
Spent $143.5 million — $122.6 million to run schools, about $12,165 per student, plus $18.6 million on buildings and equipment. Money in: $98.2 million local (mostly property tax), $36.2 million state, $10.8 million federal. Long-term debt: $35 million.
Spent $151.1 million — $135.1 million to run schools, about $15,424 per student, plus $10.1 million on buildings and equipment. Money in: $76.1 million local (mostly property tax), $54.6 million state, $25.1 million federal. Long-term debt: $39.5 million.
Spent $115.3 million — $82.4 million to run schools, about $11,048 per student, plus $24.7 million on buildings and equipment. Money in: $81.3 million local (mostly property tax), $19.9 million state, $3.7 million federal. Long-term debt: $175.1 million.
Spent $129.9 million — $87.1 million to run schools, about $14,112 per student, plus $39.1 million on buildings and equipment. Money in: $90.4 million local (mostly property tax), $13.8 million state, $3.1 million federal. Long-term debt: $60.6 million.
Spent $107.6 million — $96.8 million to run schools, about $15,871 per student, plus $7.2 million on buildings and equipment. Money in: $93.9 million local (mostly property tax), $19.9 million state, $5.2 million federal. Long-term debt: $53.1 million.
And 15 more.
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 High compared with other U.S. counties. FEMA estimates natural hazards cost St. Louis County about $752.7 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.
906 bridges in St. Louis County: 272 in good condition, 589 fair, and 45 poor (5.0%). “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.
| IS 270 E over CST CONWAY RD · built 1964 | 182,944 vehicles a day |
| IS 270 E over CST WEST PORT PLAZA DR · built 1965 | 137,112 vehicles a day |
| IS 270 E over MALINE CR · built 1931 | 111,723 vehicles a day |
| IS 170 E over RVR DES PERES · built 1968 | 97,246 vehicles a day |
| IS 64 W over CO NORTH FORTY DR TO SOR · built 1985 | 71,687 vehicles a day |
| IS 64 E over CO NORTH FORTY DR TO SOR · built 1985 | 64,631 vehicles a day |
Source: Federal Highway Administration, National Bridge Inventory (2025 submission). Includes state, county and city bridges.
Federal grants paid for $695.9 million of work in St. Louis County in fiscal 2025, about $693 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 St. Louis 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 St. Louis County built: brayden.ozark@gmail.com.
More of Missouri: the state government and every county in Missouri.
Nearby counties: St. Louis city (11 mi) · St. Charles County (16 mi) · Jefferson County (27 mi) · Monroe County, IL (29 mi) · St. Clair County, IL (30 mi) · Jersey County, IL (31 mi).