St. Mary: Demographics & People
Census counts 285 people in St. Mary, in 108 households. Population grew 11.8% from 255 (2022) to 285 (2024). Median age 48.9 years. (5.6y older than Ste. Genevieve County; 9.7y older than Missouri). Children under 18 are 20% of the population. Population is 88% White (non-Hispanic) and 3% Black. The community is relatively homogeneous (Simpson index 0.19). 59% of households are family-led. County health: 37% adult obesity, 21% smoke.
- 2.6 people per household.
- 41% non-family households (singles, roommates).
Population & Trend
Population grew 11.8% from 255 (2022) to 285 (2024) — about 19.6× the recent U.S. annual rate of ~0.6%/yr. Estimated 2026 population: ~319 (extrapolated at 5.9%/yr trend). Census Bureau Vintage estimate: 369.
| Census data vintage | 2024 |
|---|---|
| Population | 18,479 people |
| Annual growth rate · Population change | 11.8% |
| Annual growth rate · Population (2022) | 255 |
| Annual growth rate · Population (2024) | 285 |
| Annual growth rate · Population growing | Yes |
| Annual growth rate · Trend category | booming |
| Population | 285 people |
| Population Estimate | 369 |
Sources: Census ACS 5-Year 2023, Table B01003 · Refreshed 2026-04-12
Age Distribution
Median age 48.9y is 10.0 years older than the U.S. median (38.9y). Children under 18 make up 20% — below the U.S. share of ~22%.
| Age Summary · Median age | 48.9 years (vs Missouri 39.2y) |
|---|---|
| Age Summary · Children Pct | 19.6% |
| Age Summary · Character | established |
| Population under 18 | 56 |
| Median age | 48.9 years (vs Missouri 39.2y) |
Sources: Census ACS 5-Year 2023 · Refreshed 2026-04-12
Race, Ethnicity & Diversity
Of 285 residents, race / ethnicity breaks down by Census ACS counts (a person can identify with one or more groups). The Simpson diversity index is 0.19 (0 = single group, 1 = perfectly even distribution); this is read as relatively homogeneous.
| White residents | 207 |
|---|---|
| Black residents | 22 |
| Hispanic or Latino residents | 2 |
| Diversity Index · Diversity index (Simpson) | 18.8% |
| Diversity Index · Diversity label | relatively homogeneous |
| Diversity Index · Groups counted | 3 |
| Diversity Index · Largest group share | 89.6% |
| Black population | 3.2% |
| Hispanic or Latino population | 0.4% |
| White (non-Hispanic) population | 87.7% |
Sources: Census ACS 5-Year 2023 · Refreshed 2026-04-12
Ancestry
Self-reported ancestry from Census ACS — what residents report as their ethnic origin, separate from race. Counts can exceed population because people can list multiple ancestries.
Top (7)
Citizenship & Origin
Where residents were born and their citizenship status (Census ACS).
| Residents born in this state | 253 |
|---|---|
| Residents born in another state | 32 |
| Share born in this state | 88.8% |
| Share born in another state | 11.2% |
| Native-born U.S. citizens | 11.2% |
| Total foreign-born residents | 96 |
Households & Family Composition
108 households. Averaging 2.5 people each — matches the U.S. average of 2.5. 59% are family households — below the U.S. share of ~65%. Of 55 families, 16% are married couples with children.
| Children under 18 | 48 |
|---|---|
| Total families | 55 |
| Married couples with children | 9 |
| Single-parent households | 7 |
| Average household size | 2.55 |
| Women who gave birth (past year) | 17.9% |
| Grandparents living with grandchildren | 2 |
| Family households | 64 households |
| Households that are families | 59.3% |
| Total households | 108 households |
Sources: Census ACS 5-Year 2023 · Refreshed 2026-04-12
Residential Stability & Migration
How long residents have lived here and where they came from. 10.0% moved within the county in the past year — the U.S. baseline is roughly 8–10%.
| Moved within the county (past year) | 10.0% |
|---|---|
| Migration · People moving in (annual) | 17,287 |
| Migration · People moving out (annual) | 17,313 |
| Migration · Net migration (in − out) | -26 |
| Migration · Year | 2022-2023 |
Sources: IRS SOI Migration 2021-2022 · Refreshed 2026-04-12
Disability
Census ACS measures self-reported functional limitations — vision, hearing, mobility, cognitive, self-care, or independent-living. The U.S. baseline disability rate is about 12–13%; rates trend higher with median age.
| Residents with a disability | 17 |
|---|---|
| Disability rate | 7.1% |
Other
| Congressional District · District | 8 |
|---|---|
| Congressional District · Formatted | MO-08 |
| Congressional District · Congress | 118th |
| Cdc Birth Rate · Fips | 29,186 |
| Cdc Birth Rate · State Fips | 29 |
| Cdc Birth Rate · County Fips | 186 |
| Cdc Birth Rate · County | Ste Genevieve |
| Cdc Birth Rate · Birth Rate | 20.8% |
| Cdc Birth Rate · Lower Ci | 15.80 |
| Cdc Birth Rate · Upper Ci | 26.80 |
| Cdc Mortality · Fips | 29,186 |
| Cdc Mortality · County | Ste. Genevieve County |
| Cdc Mortality · Urban Rural | Noncore |
| Cdc Mortality · Total Deaths 2020 2023 | 589 |
| Cdc Vaccination · Fips | 29,186 |
| Cdc Vaccination · County | Ste. Genevieve County |
| Cdc Vaccination · Dose1 Pop Pct | 50.7% |
| Cdc Vaccination · Series Complete Pct | 46.3% |
| Cdc Vaccination · Booster Pct | 54.1% |
| Cdc Vaccination · Population 2019 | 17,894 |
| Cdc Vaccination · Metro Status | Non-metro |
| Family Score · Score | 1.50 |
| Family Score · Schools | 1 |
| Family Score · Children Pct | 19.6% |
| Family Score · Rating | limited |
| Town Summary · Key Facts | population 285, booming, established, working-class, blue collar |
| Town Summary · Population | 285 people |
| Town Summary · County | Ste. Genevieve County |
Sources: Census place-to-CD118 crosswalk (place_fips) · federal dataset cascade