ZIP Code 78666 — San Marcos city, TX Demographics & Data

ZIP code 78666 covers San Marcos, TX in Hays County with a population of about 87,775.

At a glance, the area shows median age of 27.0 versus a U.S. median of about 38.9.

It sits in telephone area codes 512, 737; U.S. House district TX-21; the AUSTIN media market.

San Marcos, TX sits in a university / college context (near texas state university (1.5 mi)). Expect stronger interest in student housing, rentals, walkability, transit, and a younger adult age mix versus typical suburban ZIPs.

Median household income in ZIP 78666 is about $55,478 — about 26% below the U.S. median ($75,149).

On socioeconomic markers, US5 shows a poverty rate of 23.3%; unemployment rate near 5.6%; 34.6% of adults with a bachelor’s degree or higher (roughly in line with the national share (33.7%)).

Labor and commute patterns include leading industry context around Food services, Education, and Retail trade; about 9.4% of workers reporting work-from-home (about 5.8 points below the U.S. share (15.2%)); a mean commute of about 180.0 minutes (U.S. average near 26.8).

Median home value is about $271,900 — about 22% below the U.S. median home value ($348,079).

Housing tenure and rents show median gross rent around $1,134 (about even with the U.S. median rent ($1,163)), and owner-occupancy near 38.4% (about 27.0 points below the national owner-occupancy rate (65.4%)).

To comfortably buy a median-priced home in ZIP 78666 in San Marcos, TX, a household would need roughly $75,000 in annual income under a 20% down, 30-year loan at 6.8% (illustrative), keeping housing costs near 28% of income. Estimated monthly PITI is about $1,747. That is about 35% above the local median household income ($55,478), so the median earner would likely stretch or need a larger down payment. Rates, taxes, insurance, and HOA fees vary — treat this as a planning estimate, not a lender quote.

FEMA’s National Risk Index rates natural-hazard risk for San Marcos city, TX as Relatively Moderate (composite score 90.6), which is among the highest nationally. The strongest component scores on US5 are flood (93.2) and wildfire (87.9). These scores are county-linked NRI values published for planning context — all ZIP codes in the same county share the same composite score on US5. Useful when comparing insurance and disaster exposure across areas, not a substitute for a parcel-level flood or fire determination.

Climate normals for San Marcos city, TX show little to no average snow and around 36.5 inches of annual precipitation.

IRS migration statistics show a net inflow of about 4,140 for ZIP 78666 (San Marcos city, TX) on US5’s published series — a signal of people/tax filers moving in relative to those leaving. Inflows often track job growth, housing demand, or lifestyle migration; treat the figure as a directional indicator rather than a precise headcount.