Boundary Atlas

ZIP code 78664: Round Rock, TX

ZIP code 78664 is in Round Rock (79% of residents) and Pflugerville (9.9%), in Williamson County (88%) and Travis County (12%), Texas. 11% of its residents live outside city limits. It is in Texas's 17th congressional district (55%), Texas's 11th congressional district (34%) and Texas's 31st congressional district (11%). Its state senate districts are State Senate District 5 (88%) and State Senate District 14 (12%); its state house districts are State House District 136 (74%), State House District 52 (14%) and State House District 46 (12%).

60,287residents (2020 Census)
16.6 sq miland area
2cities and towns
3congressional districts
18voting precincts

See it on the mapAll of Texas

City and county

City or townShare of ZIP residents
Round Rock79%
Pflugerville9.9%

CountyShare of ZIP residents
Williamson County88%
Travis County12%

Town or county subdivisionShare of ZIP residents
Round Rock-Georgetown CCD74%
Taylor CCD14%
Northeast Travis CCD12%

Congressional districts

Congressional districtShare of ZIP residents
Texas's 17th congressional district (TX-17)55%
Texas's 11th congressional district (TX-11)34%
Texas's 31st congressional district (TX-31)11%

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.

State legislative districts

State senate districtShare of ZIP residents
State Senate District 588%
State Senate District 1412%

State house districtShare of ZIP residents
State House District 13674%
State House District 5214%
State House District 4612%

Voting precincts

18 voting precincts overlap ZIP 78664. 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:78664")

ZIP 78664 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.