St. Mary's County, Maryland Population 2026
Updated April 2026 · US Census ACS 2023 5-Year Estimates · 12th-largest in Maryland
The population of St. Mary's County, Maryland is 114,372 as of the 2023 American Community Survey, making it the 12th-largest county in Maryland. The median household income is $114,580, the median home value is $390,900, and the median age is 37.0.
The population of St. Mary's County has grown 10.1% since 2010 (105,772 → 116,469), a +0.69% annualized rate.
114,372
Population
+0.69%
Annual growth
319
People / sq mi
$114,580
Median Income
$390,900
Median Home Value
St. Mary's County covers 359 sq mi of land at 319.0 people per square mile.
About St. Mary's County, MD
Among US counties, St. Mary's County stands out first on household income: a median of $114,580, above the US median of $78,538. With 114,372 residents, St. Mary's County is a county in Maryland. It ranks #12 among counties in Maryland by population.
Households here are among the highest-earning of all US counties: median income is $114,580, above the US median of $78,538. The poverty rate, 5.6%, is on the lower side for US counties and below the national 12.4%. Real estate commands a premium here — a median home value of $390,900, with typical rent around $1,692.
Educational attainment is on the higher side for US counties — 35.1% of adults hold a four-year degree, near the national 35.0%. An unusually large 15.3% of workers are remote, above the national 14.0%, and the average commute runs about 30 minutes each way.
Taken together, the income and housing figures place St. Mary's County firmly in the higher-cost, higher-earning tier of US counties — a profile that tends to track dense job markets and competitive housing.
St. Mary's County Population History (2010-2024)
The county of St. Mary's County had a population of 105,772 in 2010 and 116,469 in 2024, a 10.1% growth over 14 years. The peak was 116,469 in 2024. Average annual growth rate: 0.69%.
116,469
Population (2024)
105,772
Population (2010)
116,469
Peak (2024)
0.69%
Avg Annual Growth
| Year | Population |
|---|---|
| 2010 | 105,772 |
| 2011 | 107,589 |
| 2012 | 108,847 |
| 2013 | 109,284 |
| 2014 | 109,998 |
| 2015 | 111,092 |
| 2016 | 111,886 |
| 2017 | 112,627 |
| 2018 | 112,948 |
| 2019 | 113,764 |
| 2020 | 114,006 |
| 2021 | 114,674 |
| 2022 | 115,001 |
| 2023 | 115,479 |
| 2024 | 116,469 |
Race & Ethnicity
| White | 72.3% |
| Black or African American | 14.8% |
| Asian | 0.0% |
| Hispanic or Latino (any race) | 1.7% |
| Two or More Races | 0.0% |
Age & Sex
37.0
Median Age
49.6%
Female
50.4%
Male
13.7%
Age 65+
Age Distribution
Children (under 15): 19.8% · Seniors (65+): 13.7%
Income & Poverty
| Median household income | $114,580+$12,928 vs state |
| Mean household income | $138,624 |
| Per-capita income | $51,358 |
| Poverty rate | 5.6%-0.7% vs state |
| Unemployment rate | 2.5% |
| Employment-to-population | 63.1% |
Top Industries by Employment
The largest employment sector in St. Mary's County is public administration, accounting for 19.1% of workers.
How residents commute
1.0%
Drive alone
2.4%
Carpool
75.0%
Public transit
15.3%
Work from home
30.4 min
Avg commute
Housing
$390,900$-6,800 vs state
Median home value
$1,692
Median rent
72.6%
Homeownership rate
46,078
Total housing units
90.6%
Occupied
9.4%
Vacant
27.4%
Renter-occupied
Social & access
96.3%
With health insurance
94.9%
With broadband internet
45.1%
Foreign-born
14.1%
Veterans (18+)
11.2%
With a disability
93.1%
Speak language other than English at home
Education
92.4%
High School+
35.1%
Bachelor's+
Largest cities in Maryland
Other counties in Maryland
Part of Maryland
Metro areas in Maryland
County rankings
Frequently Asked Questions
St. Mary's County, Maryland has a population of 114,372 according to the US Census Bureau's 2023 American Community Survey 5-year estimates, making it the 12th-largest county in Maryland. Population density is 319 people per square mile.
The population of St. Mary's County has grown 10.1% since 2010 (105,772 → 116,469), a +0.69% annualized rate.
The median household income in St. Mary's County, Maryland is $114,580, with mean (average) household income of $138,624 and per-capita income of $51,358. 5.6% of residents live below the federal poverty level.
In St. Mary's County, the largest racial and ethnic groups are White (72.3%), Black or African American (14.8%), Hispanic or Latino (1.7%). Figures are from the US Census Bureau's 2023 ACS 5-year estimates and reflect self-reported responses.
The median age in St. Mary's County, Maryland is 37.0 years. Residents are 49.6% female and 50.4% male.
The median home value in St. Mary's County is $390,900 and median monthly rent is $1,692. 72.6% of occupied housing units are owner-occupied. The county has 46,078 total housing units, 9.4% of which are vacant.
The largest employment sector in St. Mary's County, Maryland is public administration, employing 19.1% of workers. The unemployment rate is 2.5%.
Baltimore is among the largest cities associated with St. Mary's County, Maryland, with a population of 577,193.
St. Mary's County, MD Climate
St. Mary's County, MD has an average annual temperature of 13.8°C (57°F) and receives about 1092 mm of precipitation per year. The warmest month is July and the coldest is January. Figures are 1970–2000 climate normals.
13.8°C
Avg Temp
1092
Precip (mm/yr)
Jul
Hottest Month
Jan
Coldest Month
| Month | Avg (°C/°F) | Precip |
|---|---|---|
| January | 2° / 36° | 87 mm |
| February | 3° / 38° | 79 mm |
| March | 8° / 46° | 103 mm |
| April | 13° / 55° | 79 mm |
| May | 18° / 64° | 106 mm |
| June | 23° / 73° | 91 mm |
| July | 25° / 77° | 102 mm |
| August | 24° / 76° | 102 mm |
| September | 21° / 70° | 98 mm |
| October | 15° / 59° | 83 mm |
| November | 10° / 49° | 81 mm |
| December | 5° / 41° | 81 mm |
1970–2000 normals from WorldClim 2.1 (~9 km grid). Precipitation can be less precise near mountains or coastlines, where rainfall varies sharply over short distances.
Best time to visit St. Mary's County, MD
The most comfortable months to visit St. Mary's County, MD are typically September, June and August, when temperatures are mildest and rainfall is relatively low. The hottest month is July (around 31°C high). The coldest is January (near -3°C low). May is usually the wettest month.
Where to stay near St. Mary's County
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Data from the American Community Survey (ACS) 5-Year estimates.
Source: U.S. Census Bureau ACS, 2026.