St. Mary's County, MD demographics:
population, income, and more

Total population
118,578
0.6% year-over-year change
Median household income
$123,406/yr
5.0% year-over-year change
Housing units
47,379
0.8% year-over-year change

St. Mary's County population

How many people live in St. Mary's County

St. Mary's County is home to 118,578 residents, according to the most recent Census data. Gender-wise, 50.4% of St. Mary's County locals are male, and 49.6% are female.

Total population
118,578
0.6% year-over-year change
Gender ratio
Male
50.4%
59,772
Female
49.6%
58,806
Value Percent YoY change
Male 59,772 50.4% 0.7%
Female 58,806 49.6% 0.5%
A higher population often means more rental variety and livelier areas. The gender balance—how many men live here compared to women—can reveal a lot about the community and the lifestyles of its residents. Use this info to get a sense of the area's pace and personality.

Age demographics

The median age in St. Mary's County is 42, with the population distributed as follows: about 19.6% are children under 15, then 13.1% are in the 15 to 24 age group. Adults between 25 and 44 make up 27.5% of the population, while another 25.8% fall into the 45 to 64 bracket. Finally, around 14.1% are 65 or older.

Median age
41.6
Age breakdown
Under 15
19.6%
15 to 24
13.1%
25 to 44
27.5%
45 to 64
25.8%
Over 65
14.1%
Value Percent YoY change
Under 15 23,236 19.6% -1.9%
15 to 24 15,507 13.1% 0.4%
25 to 44 32,579 27.5% 1.5%
45 to 64 30,536 25.8% -0.1%
Over 65 16,720 14.1% 3.8%
The age composition helps you get insight into who lives in the area. A younger population might mean a more active, fast-paced vibe, while an older one could suggest a quieter, slower lifestyle. If there's a balanced makeup, you’re likely to find a variety of services, housing types, and community spaces that cater to different life stages.

Racial makeup

In St. Mary's County, 94.1% of the population are US-born citizens, while 4.2% have gained naturalized citizenship. At the same time, 1.7% of residents are non-citizens. As for race, 71.8% of locals are Caucasian, 14.3% are African American and 2.6% have Asian roots. There’s also a share of 9.2% that includes residents with two or more races.

Citizenship
U.S.-born citizens
94.1%
Non-U.S.-born citizens
4.2%
Non-citizens
1.7%
Value Percent YoY change
U.S.-born citizens 111,582 94.1% 0.8%
Non-U.S.-born citizens 4,928 4.2% -3.1%
Non-citizens 2,068 1.7% -1.3%
Racial breakdown
White
71.8%
Black or African American
14.3%
American Indian and Alaska Native
0.1%
Asian
2.6%
Native Hawaiian and other Pacific Islander
0%
Two or more races
9.2%
Other
2%
Value Percent
White 85,148 71.8%
Black or African American 16,921 14.3%
American Indian and Alaska Native 149 0.1%
Asian 3,080 2.6%
Native Hawaiian and other Pacific Islander 6 0%
Two or more races 10,908 9.2%
Other 2,366 2%

Households in St. Mary's County

A peek inside St. Mary's County households

St. Mary's County has 43,430 households, with an average of 3 members in each. Of these, 71.4% are families, while the remaining 28.6% are made up of individuals living alone or with non-relatives, such as roommates.

Households stats

Total households
43,430
1.8% year-over-year change
Average people per household
3
Non-family households
12,427
Family households
31,003
Value Percent YoY change
Non-family households 12,427 28.6% 3.5%
Family households 31,003 71.4% 1.1%
The mix between family and non-family households gives a glimpse into daily life. A higher percentage of families might mean more parks and schools, while more non-family setups can mean flexible housing and diverse living styles. For renters, this can signal what kinds of homes are common and can help you figure out if the area matches your lifestyle.

Housing in St. Mary's County

The housing landscape of St. Mary's County

St. Mary's County's housing consists of 47,379 units, with 72.9% being detached single-family homes ideal for those wanting space. Attached options, including duplexes and townhouses, make up 10.5% and offer a more compact, shared living style. Then there are the multifamily buildings in the area, and for those seeking flexibility, non-traditional options like mobile homes account for 3.3% of the housing landscape.

Housing units
47,379
0.8% year-over-year change
Housing types
Value Percent
1 unit, detached 34,557 72.9%
1 unit, attached 4,972 10.5%
2 units 445 0.9%
3 or 4 units 470 1%
5 to 9 units 1,265 2.7%
10 to 19 units 1,676 3.5%
20 to 49 units 1,337 2.8%
50 or more units 1,074 2.3%
Mobile home 1,568 3.3%
Boat, RV, van, etc. 15 0%
Homes built since 2020
834
64.5% year-over-year change

The age of buildings in St. Mary's County

In St. Mary's County, the median construction year is 1988. About 3.4% of homes were built before the 1940s, with another 2.2% going up by 1949. Most development happened in the second half of the 20th century. Then, 19.7% of homes were added from 2000 to 2009, 15.3% between 2010 and 2019, and 1.8% are part of the newest wave of development.

Construction year breakdown by decade
Value Percent YoY change
Built in 1939 or earlier 1,624 3.4% 6.0%
Built between 1940 and 1949 1,034 2.2% -9.8%
Built between 1950 and 1959 2,219 4.7% -4.9%
Built between 1960 and 1969 2,581 5.4% 4.8%
Built between 1970 and 1979 6,521 13.8% -1.9%
Built between 1980 and 1989 7,677 16.2% 4.3%
Built between 1990 and 1999 8,330 17.6% -3.6%
Built between 2000 and 2009 9,331 19.7% -3.5%
Built between 2010 and 2019 7,228 15.3% 7.5%
Built in 2020 or later 834 1.8% 64.5%
As a renter, knowing when homes were built helps you understand the potential condition and design of rental units. Newer builds may have more contemporary layouts, while older homes can offer character or larger lots, depending on the area.

St. Mary's County occupancy rates

Out of the 43,430 occupied housing units in St. Mary's County, 73.7% are owner-occupied, while 26.3% are lived in by tenants. Meanwhile, 8.3% of all homes on the local market sit vacant.

Occupied housing units
43,430
1.8% year-over-year change
Occupancy breakdown
Renter occupied
11,427
Owner occupied
32,003
Value Percent YoY
change
Renter occupied 11,427 26.3% -0.4%
Owner occupied 32,003 73.7% 2.5%
Unoccupied housing units
8.3%
Unoccupied housing units refer to homes that are currently without residents—whether they're waiting for renters or owners, used seasonally, or simply unclaimed. A higher share of empty homes may mean more housing availability, while a low number can reflect a tighter market with more competition. This, along with the renter-vs.-owner mix, helps paint a clearer picture of what types of housing and services are likely to be available in the area.

St. Mary's County housing costs

Housing costs in St. Mary's County come to a median of $1,902 per month, while tenants specifically pay a median gross rent of $1,626.

Median housing costs per month
$1,902/month
This figure sums up typical monthly housing costs for all households in the area. If you own, it includes mortgage payments in addition to property taxes, insurance and HOA fees. If you rent, it accounts for rent plus extras like utilities. It’s useful for seeing how local living expenses stack up compared to other places.
Median gross rent in St. Mary's County
$1,626/month
Gross rent gives a more complete look at what renters actually pay, including not just base rent, but also utilities and fees. It’s a key number for evaluating rental affordability in your area of interest and understanding how it compares to nearby locations.

Education in St. Mary's County

St. Mary's County education at a glance

About 33.7% of the population in St. Mary's County went to high school, while 21.9% pursued college studies. Another 8.1% earned an associate degree and 19.3% hold a bachelor’s. Meanwhile, 14.2% went even further, earning a master’s or doctorate.

Education level
Value Percent YoY change
No high school 2,555 2.8% 0.3%
High school diploma 30,374 33.7% -4.1%
College diploma 19,722 21.9% 2.9%
Associate degree 7,278 8.1% 5.5%
Bachelor's degree 17,363 19.3% 2.0%
Graduate degree 12,823 14.2% 8.0%
A community’s education mix can offer insights into the local economy and housing market. Higher levels of education often align with more job opportunities and stable incomes, which can increase demand for homes and influence both rent prices and rental availability.

Income in St. Mary's County

How much people earn in St. Mary's County

The average annual household income in St. Mary's County was $139,830 in 2024, the most recent annual data available, according to the U.S. Census Bureau. This marked a +7.3% change from the previous year. At the same time, the median income stood at $123,406, reflecting a +5% shift over the same period.

Average household income in St. Mary's County
$139,830/year
7.3% year-over-year change
Median household income in St. Mary's County
$123,406/year
5.0% year-over-year change

St. Mary's County income by age

In St. Mary's County, households led by residents aged 25 to 44 — usually in the early to mid stages of their careers — have a median income of $138,839. Those with someone between 45 and 64 in charge, often well established professionally, earn $158,657 overall. Younger households, where the main provider is under 25 and just starting out, report a median income of $59,178, while those led by someone over 65, many of whom may be retired, have about $86,298 in earnings. Overall, 92% of the locals in this community live above the poverty line.

Income breakdown by age
Value YoY change
Under 25 $59,178 -12.5%
25 - 44 $138,839 -3.6%
45 - 64 $158,657 5.8%
Over 65 $86,298 1.4%
Above poverty level
105,611
Below poverty level
9,164
Value Percent YoY
change
Above poverty level 105,611 92% -0.2%
Below poverty level 9,164 8% 6.8%

Employment in St. Mary's County

Workforce and job types in St. Mary's County

81.6% of the working population are employed in professional or administrative positions, while 18.4% are in hands-on or service-based jobs. Also, 6.9% run their own businesses, 53% are employed by private companies, and 32.9% work in the public sector.

Workforce demographics

White collar
47,868
Blue collar
10,832
Value Percent YoY change
White collar 47,868 81.6% 1.4%
Blue collar 10,832 18.4% -3.7%
Employer type
Self employees
6.9%
Private companies
53%
Governmental workers
32.9%
Not for profit companies
7.2%
Value Percent YoY change
Self employees 4,052 6.9% -3.7%
Private companies 31,091 53% -2.8%
Governmental workers 19,301 32.9% 3.3%
Not for profit companies 4,256 7.2% 18.8%

Transportation in St. Mary's County

How people get around in St. Mary's County

In St. Mary's County, the average commute time is 77 minutes. Commuting methods vary: 95.2% of residents travel by personal vehicle and 3.4% prefer to walk, while the remaining share relies on public transit or on two wheelers to get from A to B.

Commute time
77 min
48.1% year-over-year change
Means of transportation
Value Percent YoY change
Car 47,356 95.2% -1.7%
Taxicab 49 0.1% N/A
Bus or trolleybus 466 0.9% -12.9%
Railroad 58 0.1% 93.3%
Motorcycle 21 0% 5.0%
Bicycle 88 0.2% 3.5%
Walk 1,706 3.4% 19.6%
Understanding how locals get to work can help you plan your own routine. High car usage might mean you’ll need a vehicle, while strong public transit or walkability could save you the hassle. Commute times also play a big role in quality of life—shorter trips can give you more time for the things you enjoy.

What is the median and average household income in St. Mary's County by zipcode?

Zipcode Population Number of households Median income Average income
20606 291 131 $88,262 $114,017
20609 714 341 $118,102 $304,498
20618 1,705 656 $105,508 $156,136
20619 14,212 5,719 $119,432 $137,371
20620 1,115 389 $165,972 $163,843
20621 958 534 $0 $97,222
20622 5,185 1,489 $124,063 $156,788
20624 796 296 $104,545 $116,470
20626 284 146 $0 $49,745
20628 503 199 $0 $154,709

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FAQs about St. Mary's County demographics 

What is the total population of St. Mary's County?

St. Mary's County has a total population of 118,578 residents, according to the latest release from the U.S. Census Bureau: the 2019-2023 American Community Survey (ACS) 5-year estimates. This figure changed by +0.6% compared to a year ago.

What is the gender ratio in St. Mary's County?

The gender ratio in St. Mary's County is as follows:
  • 50.4% males (59,772 residents)
  • 49.6% females (58,806 residents)

What is the median age in St. Mary's County?

The median age in St. Mary's County is 41.6.

What is the age distribution of the population in St. Mary's County?

The age distribution in St. Mary's County is as follows:
  • Under 15: 19.6% (23,236 residents)
  • Ages 15-24: 13.1% (15,507 residents)
  • Ages 25-44: 27.5% (32,579 residents)
  • Ages 45-64: 25.8% (30,536 residents)
  • Over 65: 14.1% (16,720 residents)

What is the racial and ethnic makeup of St. Mary's County?

The racial and ethnic makeup of St. Mary's County is as follows:
  • White: 71.8% (85,148 residents)
  • Black or African American: 14.3% (16,921 residents)
  • American Indian and Alaska Native: 0.1% (149 residents)
  • Asian: 2.6% (3,080 residents)
  • Native Hawaiian and Other Pacific Islander: 0% (6 residents)
  • Two or More Races: 9.2% (10,908 residents)
  • Other: 2% (2,366 residents)

What percentage of the population in St. Mary's County are U.S.-born citizens?

U.S.-born citizens represent 94.1% of the population in St. Mary's County.

How many housing units are there in St. Mary's County?

There are 47,379 housing units in St. Mary's County, reflecting a +0.8% change compared to the previous year, according to the latest data from the U.S. Census Bureau.

How many households are in St. Mary's County and what is the average household size?

St. Mary's County has a total of 43,430 households, with an average of 3 people in each.

What is the median household income in St. Mary's County?

St. Mary's County has a median household income of $123,406, representing a +5.0% shift from the previous year, according to the U.S. Census Bureau.

What is the job market overview for St. Mary's County?

Here’s a detailed breakdown of the local job market:

Job types:
  • White-collar workers: 81.6% (47,868 residents)
  • Blue-collar workers: 18.4% (10,832 residents)

Places of employment:
  • Self-employed: 6.9% (4,052 residents)
  • Private companies: 53% (31,091 residents)
  • Governmental workers: 32.9% (19,301 residents)
  • Not-for-profit companies: 7.2% (4,256 residents)

Data source & methodology

The demographic data on this page was sourced from the latest U.S. Census Bureau release—the 2019–2023 American Community Survey (ACS) 5-year estimates.

The information, issued annually, is compiled and published by the Point2Homes Research Team as soon as new data becomes available.

No representation, guarantee, or warranty is made concerning the accuracy or completeness of modified or aggregated information for particular areas.

Page last updated: September 2025