46,799 people (2024 Census estimate, −4.8% since 2020)
559 square miles of land · 84 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.
12 active community water systems list St. Mary Parish in the area they serve, reporting 62,077 people served in all (a system that crosses county lines counts its whole population).
| CITY OF MORGAN CITY WATER SYSTEM surface water · local government · LA1101005 | 12,703 served |
| WATER & SEWER COMMISSION 4 OF ST MARY surface water · local government · LA1101011 | 9,709 served |
| CITY OF PATTERSON WATER SYSTEM surface water · local government · LA1101006 | 8,456 served |
| CITY OF FRANKLIN WATER SUPPLY surface water · local government · LA1101003 | 8,325 served |
| ST MARY WATER & SEWER COMM #3 surface water · local government · LA1101010 | 7,828 served |
| ST MARY PARISH W&S #2 BAYOU VISTA buys surface water · local government · LA1101015 | 5,379 served |
| CITY OF BERWICK buys surface water · local government · LA1101014 | 5,024 served |
| ST MARY PARISH WATER SEWERAGE COMM 1 surface water · local government · LA1101009 | 2,823 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 18 people were held in St. Mary Parish's jail, in Vera's latest figure (2023), or 63 per 100,000 residents ages 15–64. In 2018 it was about 109.
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.
1 school district has its office in St. Mary Parish. School taxes are usually the largest part of a property tax bill.
Spent $118.8 million — $114.2 million to run schools, about $14,177 per student, plus $3.4 million on buildings and equipment. Money in: $58 million local (mostly property tax), $51.6 million state, $23.7 million federal. Long-term debt: $27.8 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. Mary Parish about $60.7 million a year on average in buildings, crops and lives. Ability to bounce back (community resilience): Very High; social vulnerability: Relatively High.
Source: FEMA National Risk Index (December 2025), expected annual loss. Ratings compare counties nationwide; they're estimates, not predictions.
124 bridges in St. Mary Parish: 36 in good condition, 79 fair, and 9 poor (7.3%). “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.
| LA0182 over ATCHAF.R/BERWICK BAY · built 1933 | 12,788 vehicles a day |
| LA0083 over BAYOU CHOUPIQUE · built 1978 | 10,148 vehicles a day |
| US0090 over WAX LAKE OUTLET · built 1975 | 10,035 vehicles a day |
| US0090 over BAYOU RAMOS · built 1994 | 10,035 vehicles a day |
| US0090 over BAYOU RAMOS · built 1994 | 7,885 vehicles a day |
| US0090 over RAMOS BAYOU · built 1932 | 7,504 vehicles a day |
Source: Federal Highway Administration, National Bridge Inventory (2025 submission). Includes state, county and city bridges.
Federal grants paid for $50.1 million of work in St. Mary Parish in fiscal 2025, about $1,014 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 Louisiana 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. Mary Parish 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. Mary Parish built: brayden.ozark@gmail.com.
More of Louisiana: the state government and every county in Louisiana.
Nearby counties: Iberia Parish (23 mi) · Assumption Parish (30 mi) · St. Martin Parish (35 mi) · Terrebonne Parish (42 mi) · Iberville Parish (45 mi) · St. James Parish (49 mi).