St. Mary's County Demographics

A map of St. Mary's County's Population by Race

Race	2024 Pop	2020 Pop	2024 %	2020 %
White	80,916	80,233	70.3%	70.5%
Black	16,751	15,994	14.6%	14.1%
Hispanic	7,072	6,545	6.1%	5.8%
Multiracial	6,750	6,767	5.9%	5.9%
Asian	2,989	3,301	2.6%	2.9%
Native American/Other	648	937	0.6%	0.8%

St. Mary's County, Maryland has an estimated population of 115,126, a slight increase from the 113,777 recorded in the 2020 Census. The population is 70.3% White, 14.6% Black, 6.1% Hispanic, 5.9% Multiracial, 2.6% Asian, and 0.6% Native American/Other. This demographic dot map shows the population of St. Mary's County, with one dot drawn for each person counted by the Census, color-coded by race.

St. Mary's is about as racially diverse as it was in the 2020 Census. It is considerably less diverse than Maryland overall. Demographers use a diversity index to measure the probability that two randomly selected individuals belong to different racial or ethnic groups. In St. Mary's County, that probability was 47.5% in 2020 and 47.7% in the most recent ACS estimates.

St. Mary's County is ranked the 12th most populous county in Maryland, out of 24 counties. St. Mary's County was ranked the 12th most populous county in the 2020 Census.

St. Mary's County's White Population

80,916 residents of St. Mary's County, or 70.3% of the population, identify as White. The share of White residents in St. Mary's County is significantly higher than in Maryland overall, where 46.6% of the population is White. St. Mary's County ranks 13th statewide in terms of White residents as a share of the population, out of 24 counties.

Since the 2020 Census, St. Mary's County's White population has remained roughly the same. White residents' share of St. Mary's County's population has remained roughly unchanged at 70.3%.

St. Mary's County is more White than neighboring Westmoreland County (62.3% White), Richmond County (60.1% White), Northumberland County (68.3% White), and Dorchester County (60.7% White). St. Mary's County is less White than neighboring Calvert County (73.6% White).

St. Mary's County's Black Population

16,751 residents of St. Mary's County, or 14.6% of the population, identify as Black. The share of Black residents in St. Mary's County is considerably lower than in Maryland overall, where 28.9% of the population is Black. St. Mary's County ranks 13th statewide in terms of Black residents as a share of the population, out of 24 counties.

Since the 2020 Census, St. Mary's County's Black population has grown by an estimated 4.7%. Black residents' share of St. Mary's County's population has increased from 14.1% to 14.6%.

St. Mary's County is more Black than neighboring Calvert County (11.9% Black). St. Mary's County is less Black than neighboring Westmoreland County (23.2% Black), Richmond County (26.8% Black), Northumberland County (19.1% Black), and Dorchester County (24.8% Black).

St. Mary's County's Asian Population

2,989 residents of St. Mary's County, or 2.6% of the population, identify as Asian. The share of Asian residents in St. Mary's County is slightly lower than in Maryland overall, where 6.5% of the population is Asian. St. Mary's County ranks 11th statewide in terms of Asian residents as a share of the population, out of 24 counties.

Since the 2020 Census, St. Mary's County's Asian population has declined by an estimated 9.5%. Asian residents' share of St. Mary's County's population has remained roughly unchanged at 2.6%.

St. Mary's County is more Asian than neighboring Westmoreland County (1% Asian), Calvert County (1.9% Asian), Richmond County (0.6% Asian), and Dorchester County (1.2% Asian). St. Mary's County is less Asian than neighboring Northumberland County (4.4% Asian).

St. Mary's County's Hispanic Population

7,072 residents of St. Mary's County, or 6.1% of the population, identify as Hispanic. The share of Hispanic residents in St. Mary's County is lower than in Maryland overall, where 12.5% of the population is Hispanic. St. Mary's County ranks 13th statewide in terms of Hispanic residents as a share of the population, out of 24 counties.

Since the 2020 Census, St. Mary's County's Hispanic population has grown by an estimated 8.1%. Hispanic residents' share of St. Mary's County's population has remained roughly unchanged at 6.1%.

St. Mary's County is more Hispanic than neighboring Calvert County (5.2% Hispanic), and Northumberland County (3.5% Hispanic). St. Mary's County is less Hispanic than neighboring Westmoreland County (6.4% Hispanic), and Richmond County (7.5% Hispanic).

St. Mary's County's Native American/Other Population

648 residents of St. Mary's County, or 0.6% of the population, identify as American Indian/Alaska Native/Native Hawaiian/Pacific Islander/Other. The share of Native American/Other residents in St. Mary's County is comparable to the share in Maryland overall, where 0.8% of the population is Native American/Other. St. Mary's County ranks 5th statewide in terms of Native American/Other residents as a share of the population, out of 24 counties.

Since the 2020 Census, St. Mary's County's Native American/Other population has declined by an estimated 30.8%. Native American/Other residents' share of St. Mary's County's population has remained roughly unchanged at 0.6%.

St. Mary's County is less Native American/Other than neighboring Westmoreland County (1% Native American/Other), Calvert County (0.7% Native American/Other), Richmond County (0.7% Native American/Other), Northumberland County (0.9% Native American/Other), and Dorchester County (0.8% Native American/Other).

St. Mary's County's Multiracial Population

6,750 residents of St. Mary's County, or 5.9% of the population, identify as Multiracial. The share of Multiracial residents in St. Mary's County is comparable to the share in Maryland overall, where 4.6% of the population is Multiracial. St. Mary's County ranks 2nd statewide in terms of Multiracial residents as a share of the population, out of 24 counties.

Since the 2020 Census, St. Mary's County's Multiracial population has remained roughly the same. Multiracial residents' share of St. Mary's County's population has remained roughly unchanged at 5.9%.

St. Mary's County is more Multiracial than neighboring Richmond County (4.2% Multiracial), and Northumberland County (3.7% Multiracial). St. Mary's County is less Multiracial than neighboring Westmoreland County (6% Multiracial), Calvert County (6.6% Multiracial), and Dorchester County (6.4% Multiracial).

Sources: Most recent population estimates are from the 2020-2024 American Community Survey 5-Year Estimates. 2020 population counts and map data are from 2020 Census State Redistricting Data. Geographic data are from Census TIGER/Line Shapefiles.