St. Charles County, MO population age distribution
A complete breakdown of St. Charles County's age demographics from 0 to 85 years, distributed across 18 age groups is listed in the table below.
Age Group | Population | % of Total Population |
---|---|---|
Under 5 years | 23,126 | 5.75% |
5 to 9 years | 26,302 | 6.54% |
10 to 14 years | 27,505 | 6.84% |
15 to 19 years | 26,402 | 6.56% |
20 to 24 years | 23,759 | 5.9% |
25 to 29 years | 24,085 | 5.99% |
30 to 34 years | 26,738 | 6.65% |
35 to 39 years | 28,163 | 7% |
40 to 44 years | 27,234 | 6.77% |
45 to 49 years | 25,602 | 6.36% |
50 to 54 years | 26,529 | 6.59% |
55 to 59 years | 28,553 | 7.1% |
60 to 64 years | 26,665 | 6.63% |
65 to 69 years | 21,198 | 5.27% |
70 to 74 years | 16,157 | 4.02% |
75 to 79 years | 10,853 | 2.7% |
80 to 84 years | 7,073 | 1.76% |
85 years and over | 6,433 | 1.6% |
TABLE OF CONTENTS
St. Charles County, MO population by age group
Sources: U.S. Census Bureau, American Community Survey (ACS) 2021

The largest age group in St. Charles County, MO was for the group of age 55-59 years with a population of 28,553 (7.10%), according to the 2021 American Community Survey.
At the same time, the smallest age group in St. Charles County, MO was the 85+ years with a population of 6,433 (1.60%).
St. Charles County, MO population by age cohort
To better understand the age distribution of St. Charles County, MO's population, we divided it into the following 3 cohorts:
- Children : Under the age of 18 years
- Adults (working population): Between the age of 18 and 64 years
- Seniors: 65 years and above

Here's the population for each of the three cohorts.
Age Group | Population | % of Total Population |
---|---|---|
Under 18 years | 93,754 | 23.3% |
18 to 64 years | 246,909 | 61.36% |
85 years and over | 61,714 | 15.34% |
Key stats for each age cohort as per our analysis of U.S. Census Bureau American Community Survey:
- St. Charles County's population under 18 was 23.30%, compared to the 22.51% nationwide.
- St. Charles County's working population (between 18 and 64) was 61.36%, compared to 61.45% nationwide.
- St. Charles County's elderly or the senior population (over 65 age) was 15.34% as compared to 16.04% nationwide.
St. Charles County, MO population pyramid
Population pyramid for St. Charles County, MO is charted below using the estimates from U.S. Census Bureau's American Community Survey 5-Year estimates. A wide base suggests population increase, narrow base indicates declining birth rates.
Key stats from our analysis of the St. Charles County's population pyramid:
- Youth dependency ratio, which is the number of children aged 0-14 per 100 persons aged 15-64, for St. Charles County, MO, is 29.2.
- Old-age dependency ratio, which is the number of persons aged 65 or over per 100 persons aged 15-64, for St. Charles County, MO, is 23.4.
- Total dependency ratio for St. Charles County, MO is 52.6.
- Potential support ratio, which is the number of youth (working age population) per elderly, for St. Charles County, MO is 4.3.

Here's the St. Charles County, MO's male and female population across different age groups:
Age Group | Population(Male) | Population(Female) | Total Population |
---|---|---|---|
Under 5 years | 11,732 | 11,394 | 23,126 |
5 to 9 years | 13,259 | 13,043 | 26,302 |
10 to 14 years | 14,279 | 13,226 | 27,505 |
15 to 19 years | 13,452 | 12,950 | 26,402 |
20 to 24 years | 12,176 | 11,583 | 23,759 |
25 to 29 years | 12,218 | 11,867 | 24,085 |
30 to 34 years | 13,309 | 13,429 | 26,738 |
35 to 39 years | 14,676 | 13,487 | 28,163 |
40 to 44 years | 13,285 | 13,949 | 27,234 |
45 to 49 years | 12,736 | 12,866 | 25,602 |
50 to 54 years | 13,111 | 13,418 | 26,529 |
55 to 59 years | 13,895 | 14,658 | 28,553 |
60 to 64 years | 13,180 | 13,485 | 26,665 |
65 to 69 years | 9,854 | 11,344 | 21,198 |
70 to 74 years | 7,517 | 8,640 | 16,157 |
75 to 79 years | 4,757 | 6,096 | 10,853 |
80 to 84 years | 2,930 | 4,143 | 7,073 |
85 years and over | 2,520 | 3,913 | 6,433 |
Things to know
What is the population of St. Charles County, MO under 18?
St. Charles County's population under the age of 18 is 93,754, as per the latest U.S. Census Bureau's American Community Survey estimates. This population is 23.30% of the total resident population of St. Charles County, MO.
What is the aging population in St. Charles County, MO?
St. Charles County's population aged 65 years and above was 61,714. As per the U.S. Census Bureau's American Community Survey, this population is 15.34% of the entire population.
References
- U.S. Census Bureau American Community Survey (ACS) 2017-2021 5-Year Estimates