St. Peter: Demographics & People
St. Peter's population stands at 338 people, in 128 households. Population grew 32.0% from 256 (2022) to 338 (2024). Median age 39.7 years. (2.2y younger than Fayette County; 0.6y older than Illinois). Children under 18 are 24% of the population. Population is 98% White (non-Hispanic). The community is relatively homogeneous (Simpson index 0.00). 64% of households are family-led. County is losing 437 residents per year (2022-2023). County health: 37% adult obesity, 16% smoke.
- 2.6 people per household.
- 36% non-family households (singles, roommates).
Population & Trend
Population grew 32.0% from 256 (2022) to 338 (2024) — about 53.4× the recent U.S. annual rate of ~0.6%/yr. Estimated 2026 population: ~454 (extrapolated at 16.0%/yr trend). Census Bureau Vintage estimate: 646.
| Census data vintage | 2024 |
|---|---|
| Population | 21,488 people |
| Annual growth rate · Population change | 32.0% |
| Annual growth rate · Population (2022) | 256 |
| Annual growth rate · Population (2024) | 338 |
| Annual growth rate · Population growing | Yes |
| Annual growth rate · Trend category | booming |
| Population | 338 people |
| Population Estimate | 646 |
Sources: Census ACS 5-Year 2023, Table B01003 · Refreshed 2026-04-12
Age Distribution
Median age 39.7y is 0.8 years older than the U.S. median (38.9y). Children under 18 make up 24% — above the U.S. share of ~22%.
| Age Summary · Median age | 39.7 years (vs Illinois 39.1y) |
|---|---|
| Age Summary · Children Pct | 24.0% |
| Age Summary · Character | family-oriented |
| Population under 18 | 81 |
| Median age | 39.7 years (vs Illinois 39.1y) |
Sources: Census ACS 5-Year 2023 · Refreshed 2026-04-12
Race, Ethnicity & Diversity
Of 338 residents, race / ethnicity breaks down by Census ACS counts (a person can identify with one or more groups). The Simpson diversity index is 0.00 (0 = single group, 1 = perfectly even distribution); this is read as relatively homogeneous.
| White residents | 251 |
|---|---|
| Diversity Index · Diversity label | relatively homogeneous |
| Diversity Index · Groups counted | 1 |
| Diversity Index · Largest group share | 100.0% |
| White (non-Hispanic) population | 98.2% |
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 (6)
Citizenship & Origin
Where residents were born and their citizenship status (Census ACS).
| Residents born in this state | 295 |
|---|---|
| Residents born in another state | 43 |
| Share born in this state | 87.3% |
| Share born in another state | 12.7% |
| Native-born U.S. citizens | 12.7% |
| Total foreign-born residents | 363 |
Households & Family Composition
128 households. Averaging 2.5 people each — matches the U.S. average of 2.5. 64% are family households — near the U.S. share of ~65%. Of 62 families, 31% are married couples with children.
| Children under 18 | 64 |
|---|---|
| Total families | 62 |
| Married couples with children | 19 |
| Single-parent households | 1 |
| Average household size | 2.46 |
| Women who gave birth (past year) | 15.2% |
| Grandparents living with grandchildren | 1 |
| Grandparents responsible for grandchildren | 1 |
| Family households | 82 households |
| Households that are families | 64.1% |
| Total households | 128 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. 3.6% moved within the county in the past year — the U.S. baseline is roughly 8–10%. The surrounding county is losing 437 residents per year on net (IRS migration data).
| Moved within the county (past year) | 3.6% |
|---|---|
| Migration · People moving in (annual) | 17,932 |
| Migration · People moving out (annual) | 18,369 |
| Migration · Net migration (in − out) | -437 |
| 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 | 18 |
|---|---|
| Disability rate | 6.2% |
Other
| Congressional District · District | 15 |
|---|---|
| Congressional District · Formatted | IL-15 |
| Congressional District · Congress | 118th |
| Cdc Birth Rate · Fips | 17,051 |
| Cdc Birth Rate · State Fips | 17 |
| Cdc Birth Rate · County Fips | 51 |
| Cdc Birth Rate · County | Fayette |
| Cdc Birth Rate · Birth Rate | 33.5% |
| Cdc Birth Rate · Lower Ci | 27.20 |
| Cdc Birth Rate · Upper Ci | 40.80 |
| Cdc Mortality · Fips | 17,051 |
| Cdc Mortality · County | Fayette County |
| Cdc Mortality · Urban Rural | Noncore |
| Cdc Mortality · Total Deaths 2020 2023 | 676 |
| Cdc Vaccination · Fips | 17,051 |
| Cdc Vaccination · County | Fayette County |
| Cdc Vaccination · Dose1 Pop Pct | 40.2% |
| Cdc Vaccination · Series Complete Pct | 37.0% |
| Cdc Vaccination · Booster Pct | 52.8% |
| Cdc Vaccination · Population 2019 | 21,336 |
| Cdc Vaccination · Metro Status | Non-metro |
| Family Score · Score | 7.00 |
| Family Score · Schools | 12 |
| Family Score · Children Pct | 24.0% |
| Family Score · Rating | good |
| Town Summary · Key Facts | population 338, booming, family-oriented, middle-class, mixed |
| Town Summary · Population | 338 people |
| Town Summary · County | Fayette County |
Sources: Census place-to-CD118 crosswalk (place_fips) · federal dataset cascade