Williamson County area

Population and density of Williamson County

The Census Bureau estimates that 752,827 people lived in Williamson County on July 1, 2025. That ranks #90 of 3,222 county equivalents nationally and #12 of 254 in Texas. Since the April 1, 2020 estimates base of 609,059, the population has grown by 143,768 (+23.6%), compared with +8.8% for Texas as a whole.

With 1,115.9 square miles of land, that is 675 people per square mile (260 per km²), placing Williamson County #264 nationally for density and #13 in Texas. The median county equivalent has 47 people per square mile; the Texas median is 22. Put another way, there are about 0.949 acres of land per resident.

U.S. Census Bureau, Vintage 2025 population estimates. Estimates are revised each year and are not decennial census counts. Density divides the whole population by the whole county’s land area, so it describes an average, not how settlement is distributed within the county. Population sources and methods.

Cities and towns in Williamson County

17 incorporated places lie at least partly in Williamson County. Together they are home to 558,504 people (74.2%); the other 194,323 (25.8%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Round Rock city, with 139,317 residents in the county (the city extends into 1 other county). The county seat, Georgetown city, has 106,907 residents. By land, Austin city is the largest at 324.8 mi² across all its counties. Among places with at least 1,000 residents in 2020, Liberty Hill city grew fastest since then (+276.6%).

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Williamson County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.

Metropolitan area

Williamson County is a central county of the Austin-Round Rock-San Marcos, TX Metropolitan Statistical Area. Its 5 county equivalents have 2,620,945 residents on 4,219.9 square miles of land; Williamson County accounts for 26.4% of the land and 28.7% of the residents. By combined land it ranks #67 of 393 metropolitan areas, and #25 by population.

ZIP codes

27 ZIP Code Tabulation Areas have land in Williamson County; 19 of them have most of their land inside the county, and the others mainly cover neighboring areas.

765117652776530765377657376574765777657878613786157862178626786287863378634786417864278664786657867478681787177872778728787297875078759

ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Lighter codes have less than half of their land in this county. Post-office-box and single-address ZIP Codes have no tabulation area.

Counties bordering Williamson County

Williamson County shares a land border with 6 county equivalents. It has more land than every one of them. The largest neighbor is Bell County (1,053.8 mi²) and the smallest is Lee County (629.1 mi²). Together with its neighbors, Williamson County forms a block of 6,692.6 mi² of land, of which it holds 16.7%.

How big is Williamson County compared with U.S. states?

Williamson County has more land than 1 of the 50 states. It is about 1.1 times the land area of Rhode Island (1,033.9 mi²), while Delaware, the next larger state, has 1.7 times as much land (1,948.6 mi²). Texas’s county land could hold about 234 areas the size of Williamson County.

Another way to picture it: the same land area would fill a square about 33.4 miles (53.8 km) on each side. Real county shapes are rarely square, so this is a scale reference rather than a width or driving distance.

State figures are the sums of each state’s county-equivalent land measurements in the same Census release, so states and counties are compared on the same basis. Published state totals can differ slightly because of rounding. Compare all states · Counties bigger than entire states.

What stands out about Williamson County?

Williamson County has more land than 2,657 of the other 3,221 county equivalents in the dataset.

A median is the middle county-equivalent measurement, not the average of the largest and smallest. All three bars use the same linear scale. Very small areas may appear as a thin sliver; the labels retain their values.

Does including water change its rank?

Using land plus water places Williamson County at #644 nationally by total area, 79 places farther from the top than its land rank. Other county equivalents gain more area when their water measurements are included.

Its water share is 1.4%, compared with a national county-equivalent median of 1.2% — 0.2 percentage points higher. This describes the statistical geography’s land/water mix, not flood exposure or developable land.

Closest positions in the national land ranking

These entries sit immediately beside Williamson County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

Calculated from the same Census release as the area table. Total-area order uses original ALAND + AWATER; water shares and chart labels use published square miles. Calculation details.