St. Mary's County's 2026 population is estimated at 118,449, reflecting a 0.84% growth rate over the past year (World Population Review estimate based on U.S. Census Bureau data). St. Mary's County is the 12th largest county in Maryland. The 2010 population was 105,772 and has grown 11.99% since 2010.
Data after 2023 is projected based on recent change
Overall: 37.2 years
Female: 38.1 years
Male: 36.3 years
There are 87,577 adults, (16,144 of whom are seniors) in St. Mary's County.
Female: 57,072 (49.6%)
Male: 58,054 (50.4%)
The racial composition of St. Mary's County includes 71.29% White, 14.63% Black or African American, and smaller percentages for Asian, other race, Native American, Native Hawaiian or Pacific Islander and multiracial populations.
| Race | Population ↓ | Percentage (of total) |
|---|---|---|
| White | 82,070 | 71.29% |
| Black or African American | 16,847 | 14.63% |
| Two or more races | 10,645 | 9.25% |
| Asian | 3,062 | 2.66% |
| Other race | 2,366 | 2.06% |
| Native American | 130 | 0.11% |
| Native Hawaiian or Pacific Islander | 6 | 0.01% |
St. Mary's County 's average per capita income is $75,622. Household income levels show a median of $119,446. The poverty rate stands at 7.98%.
| Name | Median ↓ | Mean |
|---|---|---|
| Married Families | $170,072 | - |
| Families | $141,221 | $162,257 |
| Households | $119,446 | $142,976 |
| Non Families | $73,545 | $89,014 |
Average Income
Median Household Income
Poverty Rate