St. Clair: Demographics & People
4,789 people call St. Clair home, in 2,034 households. Population grew 0.5% from 4,767 (2022) to 4,789 (2024). Median age 37.6 years. (4.2y younger than Franklin County; 1.6y younger than Missouri). Children under 18 are 21% of the population. Population is 90% White (non-Hispanic) and 2% Hispanic or Latino. The community is relatively homogeneous (Simpson index 0.04). 64% of households are family-led. County is gaining 2,364 residents per year (2022-2023). County health: 39% adult obesity, 17% smoke.
- 2.4 people per household.
- 36% non-family households (singles, roommates).
Population & Trend
Population grew 0.5% from 4,767 (2022) to 4,789 (2024) — close to the U.S. annual rate of ~0.6%/yr. Estimated 2026 population: ~4,811 (extrapolated at 0.2%/yr trend). Census Bureau Vintage estimate: 4,840.
| Census data vintage | 2024 |
|---|---|
| Population | 104,682 people |
| Annual growth rate · Population change | 0.5% |
| Annual growth rate · Population (2022) | 4,767 |
| Annual growth rate · Population (2024) | 4,789 |
| Annual growth rate · Population growing | Yes |
| Annual growth rate · Trend category | stable |
| Population | 4,789 people |
| Population Estimate | 4,840 |
Sources: Census ACS 5-Year 2023, Table B01003 · Refreshed 2026-04-12
Age Distribution
Median age 37.6y is 1.3 years younger than the U.S. median (38.9y). Children under 18 make up 21% — near the U.S. share of ~22%.
| Age Summary · Median age | 37.6 years (vs Missouri 39.2y) |
|---|---|
| Age Summary · Children Pct | 21.1% |
| Age Summary · Character | family-oriented |
| Population under 18 | 1,010 |
| Median age | 37.6 years (vs Missouri 39.2y) |
Sources: Census ACS 5-Year 2023 · Refreshed 2026-04-12
Race, Ethnicity & Diversity
Of 4,789 residents, race / ethnicity breaks down by Census ACS counts (a person can identify with one or more groups). The Simpson diversity index is 0.04 (0 = single group, 1 = perfectly even distribution); this is read as relatively homogeneous.
| White residents | 4,427 |
|---|---|
| Black residents | 37 |
| Asian residents | 19 |
| Hispanic or Latino residents | 36 |
| Diversity Index · Diversity index (Simpson) | 4.0% |
| Diversity Index · Diversity label | relatively homogeneous |
| Diversity Index · Groups counted | 4 |
| Diversity Index · Largest group share | 98.0% |
| Asian population | 0.3% |
| Black population | 0.6% |
| Hispanic or Latino population | 2.4% |
| White (non-Hispanic) population | 89.6% |
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 (8)
Citizenship & Origin
Where residents were born and their citizenship status (Census ACS). 1.1% are foreign-born — below the U.S. average of 13.9%. 6% have naturalized to U.S. citizenship.
| Residents born in this state | 3,409 |
|---|---|
| Residents born in another state | 1,055 |
| Share born in this state | 71.2% |
| Share born in another state | 28.8% |
| Native-born U.S. citizens | 22.0% |
| Foreign-born residents | 1.1% |
| Naturalized citizens | 5.7% |
| Total foreign-born residents | 275 |
| From Europe | 260 |
Households & Family Composition
2,034 households. Averaging 2.3 people each — smaller than the U.S. average of 2.5. 64% are family households — near the U.S. share of ~65%. Of 1,241 families, 18% are married couples with children.
| Children under 18 | 1,044 |
|---|---|
| Total families | 1,241 |
| Married couples with children | 225 |
| Single-parent households | 50 |
| Average household size | 2.34 |
| Women who gave birth (past year) | 9.4% |
| Grandparents living with grandchildren | 74 |
| Grandparents responsible for grandchildren | 15 |
| Family households | 1,294 households |
| Households that are families | 63.6% |
| Total households | 2,034 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. 15.7% moved within the county in the past year — the U.S. baseline is roughly 8–10%. The surrounding county is gaining 2,364 residents per year on net (IRS migration data).
| Moved within the county (past year) | 15.7% |
|---|---|
| Migration · People moving in (annual) | 101,499 |
| Migration · People moving out (annual) | 99,135 |
| Migration · Net migration (in − out) | 2,364 |
| Migration · Population growing | Yes |
| 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 | 487 |
|---|---|
| Disability rate | 10.3% |
Group Quarters
Group quarters are non-household living arrangements counted by the Census — college dormitories, nursing homes, military barracks, group homes, correctional facilities, and similar institutional or shared housing. 63 residents live in group quarters (1.3% of population).
| Living in group quarters | 63 |
|---|
Other
| Congressional District · District | 2 |
|---|---|
| Congressional District · Formatted | MO-02 |
| Congressional District · Congress | 118th |
| Cdc Birth Rate · Fips | 29,071 |
| Cdc Birth Rate · State Fips | 29 |
| Cdc Birth Rate · County Fips | 71 |
| Cdc Birth Rate · County | Franklin |
| Cdc Birth Rate · Birth Rate | 22.2% |
| Cdc Birth Rate · Lower Ci | 19.70 |
| Cdc Birth Rate · Upper Ci | 25.00 |
| Cdc Mortality · Fips | 29,071 |
| Cdc Mortality · County | Franklin County |
| Cdc Mortality · Urban Rural | Large fringe metro |
| Cdc Mortality · Total Deaths 2020 2023 | 3,701 |
| Cdc Vaccination · Fips | 29,071 |
| Cdc Vaccination · County | Franklin County |
| Cdc Vaccination · Dose1 Pop Pct | 62.5% |
| Cdc Vaccination · Series Complete Pct | 56.0% |
| Cdc Vaccination · Booster Pct | 46.5% |
| Cdc Vaccination · Population 2019 | 103,967 |
| Cdc Vaccination · Metro Status | Metro |
| Family Score · Score | 10 |
| Family Score · Schools | 20 |
| Family Score · Children Pct | 21.1% |
| Family Score · Rating | excellent |
| Town Summary · Key Facts | population 4,789, stable, family-oriented, working-class, blue collar |
| Town Summary · Population | 4,789 people |
| Town Summary · County | Franklin County |
Sources: Census place-to-CD118 crosswalk (place_fips) · federal dataset cascade