San Marcos: Demographics & People
San Marcos is home to 70,897 people, in 28,013 households. Population grew 2.9% from 68,920 (2022) to 70,897 (2024). Median age 25.5 years. (8.6y younger than Hays County; 9.0y younger than Texas). Children under 18 are 13% of the population. Population is 45% White (non-Hispanic) and 42% Hispanic or Latino. 42% of households are family-led. County is gaining 4,444 residents per year (2022-2023). County health: 39% adult obesity, 17% smoke.
- 2.5 people per household (vs Texas avg 2.7).
- 58% non-family households (singles, roommates) (vs Texas 35%).
- 32 dependents per 100 working-age (youth + seniors / 18-64) (vs Texas 62).
Population & Trend
Population grew 2.9% from 68,920 (2022) to 70,897 (2024) — about 4.8× the recent U.S. annual rate of ~0.6%/yr. Estimated 2026 population: ~72,946 (extrapolated at 1.4%/yr trend). Census Bureau Vintage estimate: 75,736.
| Census data vintage | 2024 |
|---|---|
| Population | 45,883 people |
| Annual growth rate · Population change | 2.9% |
| Annual growth rate · Population (2022) | 68,920 |
| Annual growth rate · Population (2024) | 70,897 |
| Annual growth rate · Population growing | Yes |
| Annual growth rate · Trend category | growing |
| Population | 70,897 people (vs Texas 143,570) |
| Population Estimate | 75,736 |
| Population Note | Census Place population covers Caldwell County, Guadalupe County, Hays County |
Sources: Census ACS 5-Year 2023, Table B01003 · Refreshed 2026-04-12
Age Distribution
Median age 25.5y is 13.4 years younger than the U.S. median (38.9y). Children under 18 make up 13% — below the U.S. share of ~22%.
| Age Summary · Median age | 25.5 years (vs Texas 34.5y) |
|---|---|
| Age Summary · Children Pct | 13.3% |
| Age Summary · Character | young community |
| Age Summary · Total Pop | 70,897 |
| Age Summary · Under 18 | 9,398 |
| Age Summary · 18 To 34 | 37,110.0× |
| Age Summary · 35 To 64 | 16,752.0× |
| Age Summary · 65 Plus | 7,637 |
| Population under 18 | 9,398 |
| Median age | 25.5 years (vs Texas 34.5y) |
Sources: Census ACS 5-Year 2024 — place-level B01001 query · Census ACS 5-Year 2023 · Refreshed 2026-04-29
Race, Ethnicity & Diversity
Of 70,897 residents, race / ethnicity breaks down by Census ACS counts (a person can identify with one or more groups).
| White residents | 43,643 |
|---|---|
| Black residents | 3,890 |
| Asian residents | 1,474 |
| Hispanic or Latino residents | 28,890 |
| Diversity Index · Simpson Index | 45.2% |
| Diversity Index · Interpretation | moderately diverse |
| Asian population | 2.1% (vs Texas 3.7%) |
| Black population | 5.2% (vs Texas 9.2%) |
| Hispanic or Latino population | 42.2% (vs Texas 36.6%) |
| White (non-Hispanic) population | 44.6% (vs Texas 36.1%) |
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). 1.4% are foreign-born — below the U.S. average of 13.9%. 9% have naturalized to U.S. citizenship.
| Residents born in this state | 47,712 |
|---|---|
| Residents born in another state | 15,715 |
| Share born in this state | 67.3% |
| Share born in another state | 32.7% |
| Native-born U.S. citizens | 22.2% |
| Foreign-born residents | 1.4% |
| Naturalized citizens | 9.1% |
| Total foreign-born residents | 5,865 |
| From Europe | 346 |
| From Asia | 39 |
| From Africa | 1,880 |
| From Latin America | 7 |
| Census Foreign Born · Caribbean | 6 |
Households & Family Composition
28,013 households. Averaging 2.2 people each — smaller than the U.S. average of 2.5. 42% are family households — below the U.S. share of ~65%. Of 12,004 families, 21% are married couples with children.
| Children under 18 | 8,514 |
|---|---|
| Total families | 12,004 |
| Married couples with children | 2,519 |
| Single-parent households | 554 |
| Average household size | 2.25 |
| Women who gave birth (past year) | 9.9% |
| Grandparents living with grandchildren | 304 |
| Grandparents responsible for grandchildren | 137 |
| Family households | 11,804 households (vs Texas 35,060) |
| Households that are families | 42.1% (vs Texas 65.3%) |
| Total households | 28,013 households (vs Texas 51,915) |
Sources: Census ACS 5-Year 2023 · Refreshed 2026-04-12
Residential Stability & Migration
How long residents have lived here and where they came from. 32.2% moved within the county in the past year — the U.S. baseline is roughly 8–10%. The surrounding county is gaining 4,444 residents per year on net (IRS migration data).
| Moved within the county (past year) | 32.2% |
|---|---|
| Migration · People moving in (annual) | 46,683 |
| Migration · People moving out (annual) | 42,239 |
| Migration · Net migration (in − out) | 4,444 |
| 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 | 3,457 |
|---|---|
| Disability rate | 5.2% |
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. 7,000 residents live in group quarters (9.9% of population).
| Living in group quarters | 7,000 |
|---|
Other
| Census Counties | Caldwell County, Guadalupe County, Hays County |
|---|---|
| Congressional District · District | 21 |
| Congressional District · Congress | 118th |
| Cdc Birth Rate · Fips | 48055 |
| Cdc Birth Rate · State Fips | 48 |
| Cdc Birth Rate · County Fips | 055 |
| Cdc Birth Rate · County | Caldwell |
| Cdc Birth Rate · Birth Rate | 34.8% |
| Cdc Birth Rate · Lower Ci | 30.40 |
| Cdc Birth Rate · Upper Ci | 39.50 |
| Cdc Mortality · Fips | 48055 |
| Cdc Mortality · County | Caldwell County |
| Cdc Mortality · Urban Rural | Large fringe metro |
| Cdc Mortality · Total Deaths 2020 2023 | 953 |
| Cdc Vaccination · Fips | 48055 |
| Cdc Vaccination · County | Caldwell County |
| Cdc Vaccination · Dose1 Pop Pct | 69.5% |
| Cdc Vaccination · Series Complete Pct | 58.1% |
| Cdc Vaccination · Booster Pct | 40.1% |
| Cdc Vaccination · Population 2019 | 43,664 |
| Cdc Vaccination · Metro Status | Metro |
| Family Score · Score | 10 |
| Family Score · Schools | 15 |
| Family Score · Childcare Centers | 16 |
| Family Score · Youth Sports Orgs | 3 |
| Family Score · Children Pct | 13.3% |
| Family Score · Rating | excellent |
| Town Summary · Key Facts | population 70,897, growing, young community, middle-class, mixed |
| Town Summary · Population | 70,897 people (vs Texas 143,570) |
| Town Summary · County | Caldwell County |
Sources: NCES school congressional district assignment · federal dataset cascade