PlainZIP

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
$54,737
Median income
$306,700
Median home value
35.7%
Bachelor's or higher

The verdict

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.

21th 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.

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 Texas average), while per-capita income is $29,465. Local economic indicators show a 23.8% poverty rate alongside 5.2% unemployment. 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 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. A geography-based comparison follows: 3 ZIP codes within about 10 miles of 78666, plus 6 more within Guadalupe County, give a clearer read than the national average alone.

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.

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 · ZIP Code Business Patterns (ZBP) As of 2023

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

Neighborhood Scorecard
Get an A-F grade across income, safety, housing, rent, education, commute, and childcare for this ZIP code.
View Scorecard →

Who lives in ZIP 78666?

26.9

Median Age

47.8%

Male

52.2%

Female

8.7%

Foreign-Born

White 57.5%
African American 5.2%
Asian 1.8%
American Indian or Alaska Native 0.5%
Native Hawaiian or Pacific Islander 0.0%
Two or More Ethnicities 25.8%
Hispanic or Latino 44.3%

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

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

$0–$20,000: 118 US ZIPs (0%). Below this entry. $20,000–$40,000: 1,573 US ZIPs (5%). Below this entry. $40,000–$60,000: 7,092 US ZIPs (23%). This entry sits in this band. $60,000–$80,000: 9,980 US ZIPs (33%). Above this entry. $80,000–$100,000: 5,778 US ZIPs (19%). Above this entry. $100,000–$120,000: 2,855 US ZIPs (9%). Above this entry. $120,000–$140,000: 1,362 US ZIPs (4%). Above this entry. $140,000–$160,000: 686 US ZIPs (2%). Above this entry. $160,000–$180,000: 364 US ZIPs (1%). Above this entry. $180,000–$200,000: 186 US ZIPs (1%). Above this entry. $200,000–$220,000: 324 US ZIPs (1%). Above this entry. This ZIP $0 $200K+ every reporting US ZIP, bucketed by value

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?

High School Graduate or Higher 59.1%
Bachelor's Degree or Higher 35.7%

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

Owner 38.1%
Renter 61.9%

$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 →

ZIP 78666 vs its nearest neighbors, by population

Resident population of this ZIP and the closest reporting ZIP codes within ~10 miles.

residents

What this shows Among its immediate neighbors, ZIP 78666 ranks the most populous - useful context the national average alone can't give.

Source U.S. Census Bureau · ACS 5-Year Estimates As of 2019–2023

ZIP 78666 vs its nearest neighbors, by median income

Median household income of this ZIP and the closest reporting ZIP codes within ~10 miles.

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.

Source U.S. Census Bureau · ACS 5-Year Estimates As of 2019–2023
ZIP Code City Population Distance
78655 Martindale, TX 2,739 8.8 mi
78640 Kyle, TX 42,954 11.5 mi
78670 Staples, TX 168 11.5 mi

More ZIP Codes in Guadalupe County

78155 standard
Seguin, TX
Pop: 45,341
78154 standard
Schertz, TX
Pop: 30,347
78108 standard
Cibolo, TX
Pop: 27,770
78124 standard
Marion, TX
Pop: 5,609
78123 standard
Mc Queeney, TX
Pop: 2,397
78638 standard
Kingsbury, TX
Pop: 2,005

Related Areas

Guadalupe County San Marcos, TX Texas

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.

Read our methodology to see how this data is sourced, computed, and verified.