St. Mary's County, MD Population By Age Group and Age Cohort in 2021 (ACS-5Yrs)

Updated on February 28, 2025.

Based on the US Census ACS-5Yrs estimates, in 2021, among the 113.21K St. Mary's County, MD population, the 55-59yrs age group constituted the highest percentage of the total population (7.35%), followed by the 15-19yrs age group (7.24%), and the 50-54yrs age group (7.20%).

In the case of age cohorts, Adults (18-64yrs) constituted the highest percentage of the total population (62.89%), followed by Children (0-17yrs) (24.27%), and Seniors (65yrs and Over) (12.84%).

The first and second charts below shows the percentage of the population by age group and age cohort respectively. The table below also shows the number and percentages for each age group and age cohort.

You can see similar information for other Maryland counties, and for Maryland.

St. Mary's County, MD Percentages of Population By Age Group in 2021
55-59yrs
15-19yrs
50-54yrs
10-14yrs
35-39yrs
30-34yrs
25-29yrs
5-9yrs
20-24yrs
Under 5yrs
St. Mary's County, MD Percentages of Population By Age Cohort in 2021
Adults (18-64yrs)
Children (0-17yrs)
Seniors (65yrs and Over)
St. Mary's County, MD Population By Age Group in 2021
0 of 0
Age Group Number of People % of Total
55-59yrs 8325 7.35
15-19yrs 8191 7.24
50-54yrs 8153 7.20
10-14yrs 8080 7.14
35-39yrs 7982 7.05
30-34yrs 7781 6.87
25-29yrs 7757 6.85
5-9yrs 7563 6.68
20-24yrs 7086 6.26
Under 5yrs 7049 6.23
45-49yrs 6958 6.15
60-64yrs 6912 6.11
40-44yrs 6841 6.04
65-69yrs 4771 4.21
70-74yrs 4087 3.61
75-79yrs 2427 2.14
80-84yrs 1644 1.45
85yrs and Over 1602 1.42
St. Mary's County, MD Population By Age Cohort in 2021
0 of 0
Age Cohort Number of People % of Total
Adults (18-64yrs) 71198 62.89
Children (0-17yrs) 27480 24.27
Seniors (65yrs and Over) 14531 12.84