ZIP Code 78666
standardSource:
San Marcos · Guadalupe County · Texas
- Population
- 63,836
- Median income
- $54,737
- Median home value
- $306,700
- Bachelor's or higher
- 35.7%
- Land area
- 457.3 sq mi
140/sq mi
▼ 28% vs US
higher than 21% of US ZIPs
▲ 10% vs US
higher than 68% of US ZIPs
Median age 26.9
Chicago
ZIP code 78666 in San Marcos, Texas has a population of 63,836. The median household income is $54,737, which is 28% below the national average. Median home value is $306,700, 10% above the US average. 35.7% of residents hold a bachelor's degree or higher.
ZIP code 78666 is classified by USPS as a standard delivery area and covers roughly 457.3 square miles in San Marcos, Guadalupe County, Texas. The area is home to 63,836 residents, producing a population density of 140 people per square mile, and falls within the Chicago time zone. These USPS and Census boundary values drive every downstream statistic on this page, including the benchmarks that compare 78666 against Texas and the nation.
On the economic side, the median household income for ZIP 78666 sits at $54,737 (28% below the Texas average), while per-capita income is $29,465. The poverty rate stands at 23.8% and the unemployment rate at 5.2%. On housing, the median home value is $306,700 (24% above the state average) with median rent at $1,319 per month, and 38.1% of occupied units are owner-occupied, a direct signal of whether 78666 behaves more like a homeowner neighborhood or a renter-heavy ZIP.
Education and household profile round out the picture: 35.7% of adults hold a bachelor's degree or higher, the median age is 26.9, and the average commute is 26 minutes. We also surface 3 nearby ZIP codes within roughly 10 miles and 6 additional ZIPs sharing Guadalupe County, so you can benchmark 78666 against its immediate geography rather than a national average alone. Every figure is sourced from the U.S. Census Bureau American Community Survey 5-Year Estimates, HUD Fair Market Rents, and FHFA Home Price Index data, no estimates, no proprietary scoring. Verify with HUD →
Top industries in ZIP 78666
Top 5 sectors by establishment count
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 + HUD FMR + FHFA HPI ACS demographics, ZBP business establishments, HUD Fair Market Rents, 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; HUD FMR + 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
$29,465
Per Capita Income
23.8%
Poverty Rate
5.2%
Unemployment Rate
25.5 min
Mean Commute Time
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?
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
$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 →
More ZIP Codes in Guadalupe County
Related Areas
Frequently Asked Questions
What county is ZIP code 78666 in? ▼
What is the population of ZIP code 78666? ▼
What is the median household income in ZIP 78666? ▼
What is the average home value in ZIP 78666? ▼
What is the demographic makeup of ZIP 78666? ▼
How many businesses are in ZIP code 78666? ▼
What are the main industries in ZIP code 78666? ▼
How have home values changed in ZIP code 78666? ▼
What is the education level in ZIP code 78666? ▼
What is the average commute time in ZIP 78666? ▼
What percentage of residents own vs. rent in ZIP 78666? ▼
What is the poverty rate in ZIP code 78666? ▼
ZIP Code Research Guides
Official Data Resources for San Marcos, TX
Verify and explore additional data for this area using these official government sources.
Source: U.S. Census Bureau, ACS 5-Year Estimates (2023). Business data: Source: Census ZIP Code Business Patterns (ZBP) 2023. Home value trends: Source: FHFA House Price Index (HPI), Five-Digit ZIP Codes.
PlainZIP is not affiliated with the U.S. Census Bureau or any government agency.
Read our methodology , how this data is sourced, computed, and verified.