San Marcos, TX · standard
ZIP Code 78666
Guadalupe County, Texas - Census ACS demographics, housing tenure, and business patterns, benchmarked against every US ZIP.
- 63,836
- 140/sq mi High-density area
- $54,737
- Median income Below-median income area
- $306,700
- Median home value Above-median home value
- 35.7%
- Bachelor's or higher Above-average bachelor's attainment
National ZIP placement
San Marcos pairs one of the lowest household incomes in the country with above-median home values, in a rural, renter-heavy and unusually populous area.
- 21st pct
- household income, US ZIPs
- Top 32%
- home value, US ZIPs
- 140
- people per sq mi
- 38%
- owner-occupied homes
Source: U.S. Census Bureau ACS 5-Year Estimates (2019–2023). Percentiles rank ZIP 78666 against every reporting US ZIP.
FHFA HPI release change
What changed in the latest House Price Index year
- FHFA House Price Index values in ZIP 78666 (San Marcos, TX) fell -6.5% from 2023 to 2024. The all-transactions index moved from 328.6 in 2023 to 307.4 in 2024 (2000 = 100).
ZIP code 78666 is a densely settled ZIP (a standard USPS delivery area) in San Marcos, Guadalupe County, Texas, with 63,836 residents across 457.3 square miles, a density of 140 people per square mile, in the Chicago time zone.
ZIP 78666 reports a modest median household income of $54,737 (28% below the average Texas ZIP), while per-capita income is $29,465. The poverty rate is 23.8%, so the area-level income figures should not be treated as typical household experience. Housing costs run above the statewide ZIP benchmark while renting is common: median home value is $306,700 (24% above the average Texas ZIP), with only 38.1% owner-occupied homes and median rent of $1,319.
A solid share of residents have a four-year degree: 35.7% of adults hold a bachelor's degree or higher, the median age is 26.9, and the average commute is 26 minutes. The page also surfaces 3 ZIP codes within roughly 10 miles and 6 more in Guadalupe County, so 78666 can be compared with both its immediate and county-level context.
Every figure on this page is sourced from the U.S. Census Bureau American Community Survey 5-Year Estimates (including median rent) and the FHFA House Price Index, no estimates, no proprietary scoring. Verify with Census →
Top industries in ZIP 78666
Top 5 sectors by establishment count in San Marcos, TX
Which industries have the most business establishments in ZIP 78666.
- Retail trade
Retail trade
393 establishments
- Accommodation and food services
Accommodation and food services
279 establishments
- Health care and social assistance
Health care and social assistance
189 establishments
- Other services (except public administration) 148
Other services (except public administration)
148 establishments
- Construction 141
Construction
141 establishments
What this shows Establishment counts come from the Census ZIP Code Business Patterns program, which counts physical business locations rather than employees or revenue.
Source: U.S. Census Bureau, American Community Survey 5-Year Estimates + ZIP Code Business Patterns + FHFA HPI ACS demographics and median rent, ZBP business establishments, FHFA HPI for ZIP 78666, San Marcos, TX · 2023 Census ACS 5-Year Estimates use a rolling 60-month sample for stable small-geography estimates; ZBP updated annually; FHFA HPI updated quarterly/annually.
Quick Facts
63,836
Population
457.3
Area (sq mi)
140
People / sq mi
Chicago
Time Zone
standard
ZIP Type
Who lives in ZIP 78666?
26.9
Median Age
47.8%
Male
52.2%
Female
8.7%
Foreign-Born
Hispanic or Latino is an ethnicity category from the Census Bureau and may overlap with other categories above.
Source: U.S. Census Bureau, ACS 5-Year Estimates (2023)
How much do residents earn?
$54,737
Median Household Income
-28% vs state ZIP avg
$29,465
Per Capita Income
23.8%
Poverty Rate
5.2%
Unemployment Rate
25.5 min
Mean Commute Time
How ZIP 78666 ranks nationally
San Marcos, TX household income vs. every US ZIP code
Median household income, the full national distribution, with this ZIP marked
$54,737 21st percentile higher than 21% of 30,318 US ZIPs
Each bar is a $20K-wide band; taller bars hold more US ZIPs. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source U.S. Census Bureau, ACS 5-Year Estimates · 2019–2023
Source: U.S. Census Bureau, ACS 5-Year Estimates (2023)
What is the education profile here?
Source: U.S. Census Bureau, ACS 5-Year Estimates (2023)
What does housing look like?
Housing stock: occupied vs vacant
36,580housing units
36,580
Total Housing Units
33,949
Occupied Units
2,631
Vacant Units
2.36
Avg Household Size
Occupancy Type
$306,700
Median Home Value
+24% vs state ZIP avg
$1,319
Median Rent
1999
Median Year Built
Source: U.S. Census Bureau, ACS 5-Year Estimates (2023)
How have home values changed over time?
FHFA House Price Index, annual appreciation data based on repeat sales and appraisals
-6.5%
YoY Change (2024)
307
HPI Index (2000 = 100)
+207%
Total Change Since 2000
Home values in ZIP 78666 have decreased 6.5% over the past year (2024). Since 2000, this ZIP has seen +207% cumulative appreciation.
| Year | Annual Change | HPI Index |
|---|---|---|
| 2020 | +5.0% | 216 |
| 2021 | +17.0% | 252 |
| 2022 | +24.6% | 314 |
| 2023 | +4.5% | 329 |
| 2024 | -6.5% | 307 |
Source: Federal Housing Finance Agency (FHFA) House Price Index, All-Transactions, Five-Digit ZIP Codes (Developmental Index). Index base = 100 in year 2000. Data through 2024. ZIP codes with few transactions may show missing values.
What businesses operate in this ZIP?
Census Bureau data shows 1,880 business establishments in ZIP 78666, employing approximately 34,315 people with a combined annual payroll of $1,555,086,000.
1,880
Businesses
34,315
Employees
$1.6B
Annual Payroll
18
Industry Sectors
| Industry | Establishments | % of Total |
|---|---|---|
| Retail trade | 393 | 20.9% |
| Accommodation and food services | 279 | 14.8% |
| Health care and social assistance | 189 | 10.1% |
| Other services (except public administration) | 148 | 7.9% |
| Construction | 141 | 7.5% |
| Professional, scientific, and technical services | 141 | 7.5% |
| Real estate and rental and leasing | 138 | 7.3% |
| Finance and insurance | 102 | 5.4% |
| Administrative and support and waste management and remediation services | 86 | 4.6% |
| Wholesale trade | 61 | 3.2% |
| Manufacturing | 57 | 3.0% |
| Transportation and warehousing | 42 | 2.2% |
| Arts, entertainment, and recreation | 32 | 1.7% |
| Information | 27 | 1.4% |
| Educational services | 27 | 1.4% |
| Mining, quarrying, and oil and gas extraction | 6 | 0.3% |
| Management of companies and enterprises | 5 | 0.3% |
| Utilities | 4 | 0.2% |
Source: U.S. Census Bureau, ZIP Code Business Patterns (ZBP), 2023. Employment figures may include noise for disclosure avoidance.
Nearby ZIP Codes
Want a side-by-side? Compare 78666 vs 78655 →
ZIP 78666 vs its nearest neighbors, by population
Resident population of this ZIP and the closest reporting ZIP codes within ~10 miles.
- 78666
San Marcos (78666)
63,836 residents
- 78640
Kyle (78640)
42,954 residents
- 78655 2,739
Martindale (78655)
2,739 residents
- 78670 168
Staples (78670)
168 residents
What this shows Among its immediate neighbors, ZIP 78666 ranks the most populous - useful context the national average alone can't give.
ZIP 78666 vs its nearest neighbors, by median income
Median household income of this ZIP and the closest reporting ZIP codes within ~10 miles.
- 78640
Kyle (78640)
$90,075 median income
- 78670
Staples (78670)
$78,625 median income
- 78655
Martindale (78655)
$55,952 median income
- 78666
San Marcos (78666)
$54,737 median income
What this shows By household income, ZIP 78666 ranks #4 of 4 neighboring ZIPs, local affluence varies block to block, not just metro to metro.
Nationwide ZIPs with similar ACS profiles
Two Census-derived peer sets for ZIP 78666, both outside TX so the neighborhoods are not geographic containment (Nearby and same-county blocks stay local).
Similar population
Nearest cross-state ZIPs by resident population (63,836 here; floor ≥1,000).
Similar median household income
Nearest cross-state ZIPs by ACS median household income.
More ZIP Codes in Guadalupe County
Related Areas
Frequently Asked Questions
What county is ZIP code 78666 in?
ZIP code 78666 (San Marcos) is located in Guadalupe County, Texas. Guadalupe County contains multiple ZIP codes, see the full list at /counties/guadalupe-tx.
What is the population of ZIP code 78666?
ZIP code 78666 in San Marcos, TX has a population of 63,836 according to the Census Bureau ACS 2023 estimates.
What is the median household income in ZIP 78666?
The median household income in ZIP 78666 is $54,737, which is 28% below the national average of $76,288.
What is the average home value in ZIP 78666?
The median home value in ZIP 78666 is $306,700, which is 10% above the national average of $278,155.
What is the demographic makeup of ZIP 78666?
The largest racial group in ZIP 78666 is White at 57.5%. Hispanic or Latino residents make up 44.3% of the population.
How many businesses are in ZIP code 78666?
ZIP code 78666 has 1,880 business establishments employing approximately 34,315 people, according to Census Bureau ZIP Code Business Patterns (ZBP) 2023 data.
What are the main industries in ZIP code 78666?
The top industries by establishment count in ZIP 78666 are: Retail trade (393), Accommodation and food services (279), Health care and social assistance (189). There are 18 industry sectors represented in total.
How have home values changed in ZIP code 78666?
According to the FHFA House Price Index, home values in ZIP 78666 decreased by 6.5% in 2024. Since 2000, home values in this ZIP have appreciated by approximately 207%. This is a developmental index based on repeat sales and appraisal data from Fannie Mae and Freddie Mac.
What is the education level in ZIP code 78666?
In ZIP code 78666, 59.1% of residents aged 25+ have a high school diploma or higher, and 35.7% hold a bachelor's degree or higher. These figures come from the Census Bureau ACS 5-Year Estimates (2023).
What is the average commute time in ZIP 78666?
The mean commute time for workers in ZIP code 78666 is 25.5 minutes according to Census ACS data. The national average is roughly 26 minutes, so commuters here spend less time traveling to work than typical.
What percentage of residents own vs. rent in ZIP 78666?
In ZIP code 78666, approximately 38.1% of occupied housing units are owner-occupied and 61.9% are renter-occupied, based on Census ACS 2023 data.
What is the poverty rate in ZIP code 78666?
The poverty rate in ZIP code 78666 is 23.8% according to Census Bureau ACS 2023 estimates. This measures the percentage of the population living below the federal poverty threshold.
Related
Take this with you
What to do with ZIP 78666's numbers, next.
- See how ZIP 78666 compares to a neighboring ZIP code on the same Census fields Compare this ZIP
- Check where San Marcos, TX ranks among every U.S. ZIP code on income, education, or homeownership View national rankings
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ZIP Code Tabulation Areas (ZCTAs) are Census Bureau approximations of USPS ZIP codes; figures describe the ZCTA area, not any single address within it.