ZIP code 78666: San Marcos, TX
ZIP code 78666 is in San Marcos (79% of residents) and Redwood (4.6%), in Hays County (91%), Guadalupe County (7.0%), Caldwell County (1.4%) and Comal County (0.2%), Texas. 17% of its residents live outside city limits. It is in Texas's 21st congressional district (80%), Texas's 27th congressional district (13%) and Texas's 35th congressional district (7.0%). Its state senate districts are State Senate District 21 (98%) and State Senate District 25 (1.8%); its state house districts are State House District 45 (90%), State House District 44 (7.0%), State House District 73 (1.8%) and State House District 17 (1.4%).
City and county
| City or town | Share of ZIP residents |
|---|---|
| San Marcos | 79% |
| Redwood | 4.6% |
| Canyon Lake | <0.1% |
| County | Share of ZIP residents |
|---|---|
| Hays County | 91% |
| Guadalupe County | 7.0% |
| Caldwell County | 1.4% |
| Comal County | 0.2% |
| Town or county subdivision | Share of ZIP residents |
|---|---|
| San Marcos CCD | 87% |
| Northeast Guadalupe CCD | 5.9% |
| Kyle-Buda CCD | 3.7% |
| Martindale CCD | 1.4% |
| Seguin CCD | 1.2% |
| Dripping Springs-Wimberley CCD | 0.7% |
| New Braunfels CCD | <0.1% |
| Canyon Lake CCD | <0.1% |
Congressional districts
| Congressional district | Share of ZIP residents |
|---|---|
| Texas's 21st congressional district (TX-21) | 80% |
| Texas's 27th congressional district (TX-27) | 13% |
| Texas's 35th congressional district (TX-35) | 7.0% |
This ZIP is split between districts. A mailing address in it could be in either; the map or locate_point gives the district for an exact address.
Elected officials
| Office | Member | Contact | Share of residents |
|---|---|---|---|
| Mayor | Jane Hughson | 79% | |
| U.S. Representative (TX-21) | Chip Roy (R) | 202-225-4236 | 80% |
| U.S. Representative (TX-27) | Michael Cloud (R) | 202-225-7742 | 13% |
| U.S. Representative (TX-35) | Greg Casar (D) | 202-225-5645 | 7.0% |
| U.S. Senator | John Cornyn (R) | 202-224-2934 · contact form | statewide |
| U.S. Senator | Ted Cruz (R) | 202-224-5922 · contact form | statewide |
| State Senator (State Senate District 21) | Judith Zaffirini (Democratic) | 956-722-2293 | 98% |
| State Senator (State Senate District 25) | Donna Campbell (R) | 830-626-0065 | 1.8% |
| State Representative (State House District 45) | Erin Zwiener (Democratic) | 90% | |
| State Representative (State House District 44) | Alan Schoolcraft (R) | 7.0% | |
| State Representative (State House District 73) | Carrie Isaac (R) | 830-730-6248 | 1.8% |
| State Representative (State House District 17) | Stan Gerdes (R) | 512-321-3720 | 1.4% |
From Wikidata (community-maintained); confirm on the city's website.
Elected in 2024 under TX's previous congressional map; this district's lines changed for the 120th Congress (seated January 3, 2027).
Officials serving now (members of Congress until January 3, 2027). Sources: State legislators: Open States (public domain); Members of Congress: the @unitedstates project, congress-legislators (CC0); Mayors: Wikidata (CC0).
Local government
- San Marcos website: https://www.sanmarcostx.gov/
- San Marcos laws: search for the San Marcos, Texas code of ordinances
- Redwood laws: search for the Redwood, Texas code of ordinances
- Hays County website: https://www.hayscountytx.gov/
- Hays County laws: search for the Hays County, Texas code of ordinances
- Guadalupe County website: https://www.guadalupetx.gov/
- Guadalupe County laws: search for the Guadalupe County, Texas code of ordinances
State legislative districts
| State senate district | Share of ZIP residents |
|---|---|
| State Senate District 21 | 98% |
| State Senate District 25 | 1.8% |
| State house district | Share of ZIP residents |
|---|---|
| State House District 45 | 90% |
| State House District 44 | 7.0% |
| State House District 73 | 1.8% |
| State House District 17 | 1.4% |
Voting precincts
31 voting precincts overlap ZIP 78666. Map them, with each precinct's share of the ZIP's residents.
Get this in your AI agent
Your agent can get these cities, counties, districts and precincts with their shares, and their GeoJSON boundaries, from Boundary Atlas. Add https://atlas-production-d344.up.railway.app/mcp to Claude, ChatGPT, Cursor or Codex (free, no key; how), then:
related_geographies(id="us:zcta:78666")
ZIP 78666 here is the Census Bureau's ZIP Code Tabulation Area, which approximates the USPS ZIP Code; PO-box-only ZIPs have none. Districts are the maps in force for the November 3, 2026 election.