St. Marys: Demographics & People
Census counts 2,788 people in St. Marys, in 905 households. Population shrank 0.2% from 2,795 (2022) to 2,788 (2024). Median age 26.6 years. (9.2y younger than Pottawatomie County; 10.9y younger than Kansas). Children under 18 are 25% of the population. Population is 79% White (non-Hispanic) and 10% Hispanic or Latino. The community is relatively homogeneous (Simpson index 0.18). 80% of households are family-led. County is gaining 243 residents per year (2022-2023). County health: 31% adult obesity, 13% smoke.
- 3.1 people per household.
- 20% non-family households (singles, roommates).
Population & Trend
Population shrank 0.2% from 2,795 (2022) to 2,788 (2024). Estimated 2026 population: ~2,781 (extrapolated at -0.1%/yr trend). Census Bureau Vintage estimate: 2,771.
| Census data vintage | 2024 |
|---|---|
| Population | 25,348 people |
| Annual growth rate · Population change | -0.2% |
| Annual growth rate · Population (2022) | 2,795 |
| Annual growth rate · Population (2024) | 2,788 |
| Annual growth rate · Trend category | stable |
| Population | 2,788 people |
| Population Estimate | 2,771 |
Sources: Census ACS 5-Year 2023, Table B01003 · Refreshed 2026-04-12
Age Distribution
Median age 26.6y is 12.3 years younger than the U.S. median (38.9y). Children under 18 make up 25% — above the U.S. share of ~22%.
| Age Summary · Median age | 26.6 years (vs Kansas 37.5y) |
|---|---|
| Age Summary · Children Pct | 25.0% |
| Age Summary · Character | young community |
| Population under 18 | 697 |
| Median age | 26.6 years (vs Kansas 37.5y) |
Sources: Census ACS 5-Year 2023 · Refreshed 2026-04-12
Race, Ethnicity & Diversity
Of 2,788 residents, race / ethnicity breaks down by Census ACS counts (a person can identify with one or more groups). The Simpson diversity index is 0.18 (0 = single group, 1 = perfectly even distribution); this is read as relatively homogeneous.
| White residents | 2,475 |
|---|---|
| Black residents | 20 |
| Asian residents | 27 |
| Hispanic or Latino residents | 230 |
| Diversity Index · Diversity index (Simpson) | 18.4% |
| Diversity Index · Diversity label | relatively homogeneous |
| Diversity Index · Groups counted | 4 |
| Diversity Index · Largest group share | 89.9% |
| Asian population | 2.4% |
| Black population | 0.5% |
| Hispanic or Latino population | 9.6% |
| White (non-Hispanic) population | 79.2% |
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). 0.9% are foreign-born — below the U.S. average of 13.9%. 4% have naturalized to U.S. citizenship.
| Residents born in this state | 1,340 |
|---|---|
| Residents born in another state | 1,307 |
| Share born in this state | 48.1% |
| Share born in another state | 51.9% |
| Native-born U.S. citizens | 46.9% |
| Foreign-born residents | 0.9% |
| Naturalized citizens | 4.2% |
| Total foreign-born residents | 72 |
| From Europe | 3 |
| From Africa | 28 |
Households & Family Composition
905 households. Averaging 3.3 people each — larger than the U.S. average of 2.5. 80% are family households — above the U.S. share of ~65%. Of 639 families, 37% are married couples with children.
| Children under 18 | 795 |
|---|---|
| Total families | 639 |
| Married couples with children | 235 |
| Average household size | 3.31 |
| Women who gave birth (past year) | 5.3% |
| Grandparents living with grandchildren | 4 |
| Family households | 722 households |
| Households that are families | 79.8% |
| Total households | 905 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. 14.3% moved within the county in the past year — the U.S. baseline is roughly 8–10%. The surrounding county is gaining 243 residents per year on net (IRS migration data).
| Moved within the county (past year) | 14.3% |
|---|---|
| Migration · People moving in (annual) | 27,451 |
| Migration · People moving out (annual) | 27,208 |
| Migration · Net migration (in − out) | 243 |
| 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 | 131 |
|---|---|
| Disability rate | 5.0% |
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. 66 residents live in group quarters (2.4% of population).
| Living in group quarters | 66 |
|---|
Other
| Congressional District · District | 1 |
|---|---|
| Congressional District · Formatted | KS-01 |
| Congressional District · Congress | 118th |
| Cdc Birth Rate · Fips | 20,149 |
| Cdc Birth Rate · State Fips | 20 |
| Cdc Birth Rate · County Fips | 149 |
| Cdc Birth Rate · County | Pottawatomie |
| Cdc Birth Rate · Birth Rate | 10.8% |
| Cdc Birth Rate · Lower Ci | 8.10 |
| Cdc Birth Rate · Upper Ci | 14.20 |
| Cdc Mortality · Fips | 20,149 |
| Cdc Mortality · County | Pottawatomie County |
| Cdc Mortality · Urban Rural | Small metro |
| Cdc Mortality · Total Deaths 2020 2023 | 496 |
| Cdc Vaccination · Fips | 20,149 |
| Cdc Vaccination · County | Pottawatomie County |
| Cdc Vaccination · Dose1 Pop Pct | 48.6% |
| Cdc Vaccination · Series Complete Pct | 44.0% |
| Cdc Vaccination · Booster Pct | 59.1% |
| Cdc Vaccination · Population 2019 | 24,383 |
| Cdc Vaccination · Metro Status | Metro |
| Family Score · Score | 10 |
| Family Score · Schools | 20 |
| Family Score · Children Pct | 25.0% |
| Family Score · Rating | excellent |
| Town Summary · Key Facts | population 2,788, stable, young community, upper-middle, mixed |
| Town Summary · Population | 2,788 people |
| Town Summary · County | Pottawatomie County |
Sources: Census place-to-CD118 crosswalk (place_fips) · federal dataset cascade