St. Mary's County MD Information


St. Mary's County Subdivisions

St. Mary's County MD Data & Demographics (As of July 1, 2018)


Total Population 116,380
Population in Households 113,581
Population in Familes 95,651
Population in Group Qrtrs 2,799
Population Density2 326
Diversity Index3 45


Median Household Income $87,651
Average Household Income $105,427
Per Capita Income $38,320


Total Housing Units 46,014 (100%)
Owner Occupied HU 28,667 (62.3%)
Renter Occupied HU 12,701 (27.6%)
Vacant Housing Units 4,646 (10.1%)
Median Home Value $332,414
Average Home Value $380,922


Total Households 41,368
Average Household Size 2.75
Family Households 29,492
Average Family Size 3
  1. If the ratio of the TDP to Total Population is greater than 1, the location gains population during the day when commuting workers are present. If the ratio is less than 1, the location is more of a bedroom community where people commute to another place for work.
  2. Population Density = Total Population per square mile.
  3. The Diversity Index is a scale of 0 to 100 that represents the likelihood that two persons, chosen at random from the same area, belong to different race or ethnic groups. If an area's entire population belongs to one race AND one ethnic group, then the area has zero diversity. An area's diversity index increases to 100 when the population is evenly divided into two or more race/ethnic groups.


2010-2017 2017-2022
Population 1.24% 1.17%
Households 1.16% 1.12%
Families 1.04% 1.02%
Median Household Income   2.89%
Per Capita Income   3.22%


St. Mary's County MD - Peer Comparisons by Rank and Percentile

The table below compares St. Mary's County to the other 24 counties / independent cities and county equivalents in Maryland by rank and percentile using July 1, 2018 data. The location Ranked # 1 has the highest value. A location that ranks higher than 75% of its peers would be in the 75th percentile of the peer group.

Variable Description Rank Percentile
Total Population # 12 54th
Population Density # 13 50th
Diversity Index # 13 50th
Median Household Income # 9 67th
Per Capita Income # 10 63rd

Additional comparisons and rankings can be made with a VERY EASY TO USE Maryland Census Data Comparison Tool.