What county is Round Rock, TX in?
Updated · Data: U.S. Census Bureau
Round Rock, Texas is in 2 counties. Most residents (98.1%) live in the Williamson County part; the rest live in Travis County.
Which counties do Round Rock residents live in?
| County | Share of residents | Chart |
|---|---|---|
| Williamson County | 98.1% (121,984 people) | |
| Travis County | 1.9% (2,304 people) |
How is Round Rock's land split between counties?
| County | Share of land area | Chart |
|---|---|---|
| Williamson County | 97.8% | |
| Travis County | 2.2% |
Inside Round Rock, the county depends on the address: check your address privately. See all Texas cities in more than one county or look up another city.
Round Rock at a glance
What ZIP codes are in Round Rock?
6 ZIP codes use the name Round Rock or are centered in it. Shares are of each ZIP's land; a ZIP named after a town can reach beyond its city limits.
| ZIP | Post office name | County (land share) |
|---|---|---|
| 78664 | Round Rock | Williamson County 86%, Travis County 14% |
| 78665 | Round Rock | Williamson County |
| 78680 | Round Rock | Williamson County |
| 78681 | Round Rock | Williamson County |
| 78682 | Round Rock | Williamson County |
| 78683 | Round Rock | Williamson County |
About Williamson County
County seat: Georgetown. FIPS code 48491. Population 643,889. All Williamson County facts.
Towns near Round Rock
- Brushy Creek: 4.6 mi away, Williamson County
- Wells Branch: 5.8 mi away, Travis County
- Pflugerville: 6.5 mi away, Travis County
- Hutto: 7.2 mi away, Williamson County
- Cedar Park: 9.3 mi away, Williamson County
- Georgetown: 10 mi away, Williamson County
Round Rock has about 124,288 people. It is an incorporated city or town.
Sources: ACS 2019-2023 5-year (residents by county, table B01003); Census TIGER/Line 2024 and Gazetteer 2024 (land, location); Census 2020 ZCTA file and GeoNames (ZIP codes). Data as of November 1, 2026. Not affiliated with any government agency.
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