160,308 people (2024 Census estimate, −0.1% since 2020)
722 square miles of land · 222 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.
21 active community water systems list St. Clair County in the area they serve, reporting 119,535 people served in all (a system that crosses county lines counts its whole population).
| PORT HURON, CITY OF surface water · local government · MI0005480 | 28,983 served |
| PORT HURON TOWNSHIP buys surface water · local government · MI0005490 | 10,654 served |
| FORT GRATIOT TOWNSHIP buys surface water · local government · MI0002385 | 10,640 served |
| MARYSVILLE, CITY OF surface water · local government · MI0004160 | 9,959 served |
| CLAY TOWNSHIP buys surface water · local government · MI0001450 | 9,866 served |
| IRA TOWNSHIP surface water · local government · MI0003390 | 6,510 served |
| ST. CLAIR WATER AND SEWER AUTHORITY surface water · local government · MI0006284 | 5,847 served |
| ST. CLAIR, CITY OF surface water · local government · MI0006270 | 5,464 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 362 people were held in St. Clair County's jail, in Vera's latest figure (2023), or 359 per 100,000 residents ages 15–64. In 2018 it was about 472.
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.
7 school districts have their office in St. Clair County. School taxes are usually the largest part of a property tax bill.
Spent $118.8 million — $110.4 million to run schools, about $15,215 per student, plus $3.8 million on buildings and equipment. Money in: $30.4 million local (mostly property tax), $75.1 million state, $19.1 million federal. Long-term debt: $106.7 million.
Spent $87.7 million — $78 million to run schools, about $14,363 per student, plus $4.5 million on buildings and equipment. Money in: $32.6 million local (mostly property tax), $60.3 million state, $7 million federal. Long-term debt: $137.7 million.
Spent $81.5 million — $52.4 million to run schools, about $14,213 per student, plus $26.3 million on buildings and equipment. Money in: $24.8 million local (mostly property tax), $32.6 million state, $5.1 million federal. Long-term debt: $74.7 million.
Spent $37.9 million — $31.3 million to run schools, about $11,802 per student, plus $2.8 million on buildings and equipment. Money in: $10.9 million local (mostly property tax), $27 million state, $1.9 million federal. Long-term debt: $69.8 million.
Spent $30.3 million — $24.3 million to run schools, about $13,836 per student, plus $4.7 million on buildings and equipment. Money in: $8.7 million local (mostly property tax), $17.8 million state, $3 million federal. Long-term debt: $21.2 million.
Spent $22.9 million — $18.9 million to run schools, about $13,834 per student, plus $2.2 million on buildings and equipment. Money in: $10.6 million local (mostly property tax), $11.7 million state, $2.2 million federal. Long-term debt: $16.2 million.
Spent $13.2 million — $11.5 million to run schools, about $15,511 per student, plus $935,000 on buildings and equipment. Money in: $3.4 million local (mostly property tax), $7.8 million state, $1.7 million federal. Long-term debt: $10.2 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 Moderate compared with other U.S. counties. FEMA estimates natural hazards cost St. Clair County about $49.4 million a year on average in buildings, crops and lives. Ability to bounce back (community resilience): Very High; social vulnerability: Relatively Low.
Source: FEMA National Risk Index (December 2025), expected annual loss. Ratings compare counties nationwide; they're estimates, not predictions.
326 bridges in St. Clair County: 130 in good condition, 165 fair, and 31 poor (9.5%). “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.
| I-94 WB over M-25 CONN · built 1964 | 21,619 vehicles a day |
| YALE ROAD over S BR MILL CREEK DRAIN · built 1989 | 2,602 vehicles a day |
| SHEA ROAD over BEAUBIEN CREEK DRAIN · built 1963 | 2,500 vehicles a day |
| GRISWOLD ROAD over PINE RIVER · built 1990 | 2,030 vehicles a day |
| ANCHOR BAY DRIVE over UNNAMED CANAL · built 1980 | 1,655 vehicles a day |
| SPARLING ROAD over PINE RIVER · built 1988 | 1,390 vehicles a day |
Source: Federal Highway Administration, National Bridge Inventory (2025 submission). Includes state, county and city bridges.
Federal grants paid for $23.4 million of work in St. Clair County in fiscal 2025, about $146 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 Michigan 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. Clair 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. Clair County built: brayden.ozark@gmail.com.
More of Michigan: the state government and every county in Michigan.
Nearby counties: Macomb County (22 mi) · Lapeer County (30 mi) · Sanilac County (36 mi) · Oakland County (41 mi) · Genesee County (53 mi) · Wayne County (54 mi).