2017 Growth Rate
0.65%
County Website
State
Founded
January 24, 1637
County Seat
Leonardtown
Lat/Lng
St. Mary's County, Maryland's estimated population is 112,413 with a growth rate of 0.65% in the past year according to the most recent United States census data. St. Mary's County, Maryland is the 12th largest county in Maryland.
| Year | Population | Growth | Growth Rate |
| 2018 | 112,664 | 251 | 0.22% |
| 2017 | 112,413 | 724 | 0.65% |
| 2016 | 111,689 | 724 | 0.65% |
| 2015 | 110,965 | 1,039 | 0.95% |
| 2014 | 109,926 | 698 | 0.64% |
| 2013 | 109,228 | 423 | 0.39% |
| 2012 | 108,805 | 1,247 | 1.16% |
| 2011 | 107,558 | 1,796 | 1.70% |
| 2010 | 105,762 | 29,788 | 39.21% |
| 1990 | 75,974 | 16,079 | 26.85% |
| 1980 | 59,895 | 12,507 | 26.39% |
| 1970 | 47,388 | 8,473 | 21.77% |
| 1960 | 38,915 | 9,804 | 33.68% |
| 1950 | 29,111 | 14,485 | 99.04% |
| 1940 | 14,626 | -563 | -3.71% |
| 1930 | 15,189 | -923 | -5.73% |
| 1920 | 16,112 | -918 | -5.39% |
| 1910 | 17,030 | -152 | -0.88% |
| 1900 | 17,182 | 1,363 | 8.62% |
| 1890 | 15,819 | -1,115 | -6.58% |
| 1880 | 16,934 | 1,990 | 13.32% |
| 1870 | 14,944 | -269 | -1.77% |
| 1860 | 15,213 | 1,515 | 11.06% |
| 1850 | 13,698 | 474 | 3.58% |
| 1840 | 13,224 | -235 | -1.75% |
| 1830 | 13,459 | 485 | 3.74% |
| 1820 | 12,974 | 180 | 1.41% |
| 1810 | 12,794 | -905 | -6.61% |
| 1800 | 13,699 | -1,845 | -11.87% |
| 1790 | 15,544 | 0.00% |
| Race | Population | Percentage |
| White | 87,485 | 78.83% |
| Black or African American | 15,922 | 14.35% |
| Two or More Races | 3,561 | 3.21% |
| Asian | 3,079 | 2.77% |
| Some Other Race | 684 | 0.62% |
| American Indian and Alaska Native | 220 | 0.20% |
| Native Hawaiian and Other Pacific Islander | 28 | 0.03% |
36.5
36.1
36.9
There are 83,491 adults, (13,184 of whom are seniors) in St. Mary's County, Maryland.
Female
55,559
50.06%
Male
55,420
49.94%
| Type | Count | Average Size | Owned |
| All | 39,276 | 2.75 | 71.9 |
| Married | 21,583 | 3.36 | 84.8 |
| Non Family | 11,630 | 1.28 | 57.9 |
| Female | 4,729 | 3.45 | 48.7 |
| Male | 1,334 | 3.24 | 69.3 |
| Education Attained | Count | Percentage |
| Less Than 9th Grade | 2,404 | 3.29% |
| 9th to 12th Grade | 5,125 | 7.02% |
| High School Graduate | 21,776 | 29.82% |
| Some College | 15,543 | 21.28% |
| Associates Degree | 5,951 | 8.15% |
| Bachelors Degree | 13,009 | 17.81% |
| Graduate Degree | 9,223 | 12.63% |
| Name | Total | High School | Bachelors |
| White | 56,644 | 52,296 | 18,519 |
| Black | 10,212 | 8,008 | 1,335 |
| Hispanic | 2,935 | 2,374 | 941 |
| Asian | 2,247 | 1,943 | 1,185 |
| Multiple Races | 985 | 905 | 304 |
| Other Race | 487 | 382 | 145 |
| Native American | 192 | 158 | 23 |
| Islander | 11 | 11 | 11 |
The highest rate of high school graduation is among islander people with a rate of 100.00%.
The highest rate of bachelors degrees is among islander people with a rate of 100.00%.
$54,379
Average Earnings
$69,864
Average Male
$40,154
Average Female
93.10% of St. Mary's County, Maryland residents speak only English, while 6.90% speak other languages. The non-English language spoken by the largest group is Spanish, which is spoken by 2.64% of the population.
| Name | Total | In Poverty | Poverty Rate |
| White | 81,098 | 4,630 | 5.71% |
| Black | 15,282 | 2,822 | 18.47% |
| Hispanic | 5,252 | 623 | 11.86% |
| Multiple | 3,486 | 604 | 17.33% |
| Asian | 3,002 | 224 | 7.46% |
| Other | 675 | 59 | 8.74% |
8.20%
Overall Poverty Rate
6.37%
Male Poverty Rate
10.00%
Female Poverty Rate
The race most likely to be in poverty in St. Mary's County, Maryland is Black, with 18.47% below the poverty level.
The race least likely to be in poverty in St. Mary's County, Maryland is White, with 5.71% below the poverty level.
The poverty rate among those that worked full-time for the past 12 months was 1.25%. Among those working part-time, it was 10.14%, and for those that did not work, the poverty rate was 16.13%.
51.9%
Overall Marriage Rate
53.2%
Male Marriage Rate
50.7%
Female Marriage Rate
The age group where males are most likely to be married is 45-54, while the female age group most likely to be married is 35-44.
| Name | Veterans | % of Total |
| White | 9,044 | 13.82% |
| Black | 968 | 8.18% |
| Hispanic | 557 | 16.12% |
| Asian | 175 | 7.46% |
| 2 or More | 147 | 11.79% |
| Other | 114 | 23.80% |
| Indian | 24 | 12.50% |
2.37%
Veteran Poverty Rate
17.84%
Veteran Disability Rate
67.4%
Labor Force Participation
62.4%
Employment Rate
4.2%
Unemployment Rate
Non citizens include legal permanent residents (green card holders), international students, temporary workers, humanitarian migrants, and illegal immigrants.
95.50%
Native Born
4.50%
Foreign Born
1.84%
Non Citizen
95.50% of St. Mary's County, Maryland residents were born in the United States, with 51.68% having been born in Maryland. 1.84% of residents are not US citizens. Of those not born in the United States, the largest percentage are from Asia.
| City | 2010 Census | 2016 Estimated | Growth | Growth Rate |
| Leonardtown | 2962 | 3769 | 807 | 27.25% |