Williamson County, Texas

Williamson County is a county in Texas, United States, immediately north of Austin along
Interstate 35. It had a population of 609,017 at the 2020 census, an estimated 752,827 by 2025,
and covers 1,118 square miles (2,900 km2) centred near 30°39′N 97°35′W.

Georgetown is the county seat; its postal code is 78626. The county holds 14 incorporated
cities and towns, 4 census-designated places and roughly three dozen smaller unincorporated
communities, and it runs on Central Time. Its FIPS code is 48491.

Towns & Villages in Williamson County

Williamson County has 14 incorporated cities and towns, 4 census-designated places (CDPs)
with population counts of their own, and dozens more crossroads and rural place names carried
on federal maps but with no government or population count. CDP stands for census designated
place, a populated area the Census Bureau tracks but that has never incorporated.

Beyond those 18 places, the USGS Geographic Names Information System records roughly three
dozen more rural communities and historic crossroads in Williamson County with no population or
ZIP of their own — among them Andice, Anderson Mill, Beaukiss, Circleville, Corn Hill,
Elm Grove, Friendship, Jonah, Macedonia, Noack, Pond Springs, Schwertner, Shiloh, Sun City,
Walburg and Weir’s older neighbor Theon. Most are no more than a church, a cemetery and a
handful of houses at a road junction; some, like Anderson Mill and Pond Springs, have been
absorbed into Cedar Park’s and Austin’s built-up edges.

Three cities on this list straddle a county line. Bartlett sits mostly in Bell County —
its downtown core is on the Bell side — but a slight majority of its incorporated land
area lies in Williamson, so the city appears in both counties’ totals. Cedar Park is
overwhelmingly a Williamson County city with only a small southern edge reaching into Travis
County, and Leander is split between the two counties as well, with the larger share on the
Williamson side. Jollyville, once a separate CDP in the county’s southeast corner, was
annexed by the City of Austin and no longer appears as its own census place.

ZIP Codes

• 78626 — Georgetown (also serves 78627, 78628 and 78633)
• 78664 — Round Rock (also serves 78665 and 78680–78683)
• 78613 — Cedar Park (also serves 78630)
• 78641 — Leander (also serves 78646)
• 78634 — Hutto
• 76574 — Taylor
• 78642 — Liberty Hill
• 76537 — Jarrell
• 76530 — Granger
• 76527 — Florence
• 76511 — Bartlett (shared with Bell County)
• 76578 — Thrall
• 78674 — Weir
• 78615 — Coupland
• 78717 — Brushy Creek (shares Round Rock’s post office)

Sonterra, Santa Rita Ranch and Serenada have no ZIP code of their own; mail addressed there
is delivered under Leander’s or Liberty Hill’s postal codes depending on the exact
location.

Geography

Interstate 35 bisects Williamson County roughly north to south, and the highway also marks a
rough dividing line between two landscapes. West of I-35 the county rises into the eastern edge
of the Texas Hill Country, limestone terrain with thin soil and scattered cedar. East of I-35 it
flattens into the Blackland Prairie, dark, fertile clay soil that made the county’s early
cotton economy possible. Of the county’s 1,134 square miles, 1,118 are land and 16 are
water, about 1.4 percent. The South San Gabriel and North San Gabriel Rivers join near
Georgetown to form the San Gabriel River, the county’s principal waterway, dammed upstream
of Georgetown to form Lake Georgetown.

Bell County lies to the north, Milam County to the northeast, Lee and Bastrop Counties to the
southeast, Travis County to the south, and Burnet County to the west. Bell County, Milam County, Lee County, Bastrop County, Travis County and Burnet County all border Williamson
directly.

Demographics

Williamson County had a population of 609,017 at the 2020 census, and the latest estimate
puts the county near 752,827 residents, among the fastest-growing counts in Texas over that
span. Round Rock and Georgetown are the two largest communities, together holding roughly a
third of the county’s population, with Cedar Park and Leander close behind. Median
household income runs $111,340, well above Texas’s statewide figure of $75,780. Population
density works out to about 545 people per square mile of land, a sharp contrast between the
built-up I-35 corridor and the sparsely settled west and northeast.

Economy & Local Life

Professional, scientific and technical services employs the most workers in the county, about
52,425 people, followed by retail trade at 41,351 and health care and social assistance at
40,580. Dell Technologies, headquartered in Round Rock since 1994, remains the county’s
best-known employer, with several thousand workers on its Round Rock campus alongside major
regional operations for Cintas, IKEA and Emerson Process Management. Taylor is home to a $17
billion Samsung semiconductor fabrication plant, announced in 2021 and expected to bring about
2,000 jobs to the county’s eastern side. Georgetown’s Southwestern University, founded
in 1840, is Texas’s oldest institution of higher education, and the city’s Sun City
Texas is one of the state’s largest age-restricted retirement communities. Georgetown’s
biggest annual event is the Red Poppy Festival each April, marking the city’s status as the
official Red Poppy Capital of Texas.

History

The Texas Legislature created Williamson County on March 13, 1848, from land previously part
of Milam County. It was named for Robert McAlpin Williamson, known as “Three-Legged
Willie” for a leg brace he wore after a childhood illness, a veteran of the Battle of San
Jacinto and later a Republic of Texas judge and legislator. Georgetown was designated the county
seat the same year.

The county holds two of the deadliest weather records in Texas history. In September 1921, a
stalled tropical storm dropped as much as 38.2 inches of rain over Thrall in 24 hours, a US
rainfall record at the time, and the resulting floods killed more than 200 people statewide. On
May 27, 1997, an F5 tornado struck the Double Creek Estates subdivision near Jarrell, destroying
every home in its path and killing 27 people, one of the deadliest single tornadoes in Texas
history.

Getting There

Interstate 35 crosses the county from south to north through Round Rock, Georgetown and
Jarrell. US 79 and US 183 also cross the county, along with State Highways 29, 45, 95, 130 and
138 and several toll roads serving the Austin metro area.

• Austin — about 25 miles south of Georgetown
• Temple — about 35 miles north
• Waco — about 65 miles north
• Bryan-College Station — about 60 miles east

Austin-Bergstrom International Airport, about 30 miles south of Georgetown, is the nearest
major commercial airport. Georgetown Municipal Airport handles general aviation. Amtrak’s
Texas Eagle stops at the Taylor station on East First Street, the county’s only passenger
rail service, connecting to Austin, San Antonio, Dallas and Chicago.

Frequently Asked Questions

Where is Williamson County located?
It sits in Central Texas immediately north of Austin, split by Interstate 35 between Hill
Country limestone to the west and Blackland Prairie to the east.

What is the population of Williamson County?
609,017 at the 2020 census, with an estimate near 752,827 by 2025.

How big is Williamson County?
1,134 square miles (2,940 km2) in total, of which 1,118 square miles are land.

What is the county seat of Williamson County?
Georgetown, designated in 1848, is the county seat; Round Rock is the county’s largest
city.

How many towns and cities are in Williamson County?
14 incorporated cities and towns, four census-designated places, and roughly three dozen
unincorporated communities and crossroads with no government of their own.

What ZIP codes does Williamson County use?
78626 for Georgetown, 78664 for Round Rock, 78613 for Cedar Park, 78641 for Leander, and separate
codes for each of the county’s smaller cities, listed above.

What is Williamson County known for?
Dell’s Round Rock headquarters, the new Samsung chip plant in Taylor, Southwestern
University in Georgetown, and the 1921 Thrall flood and 1997 Jarrell tornado, two of the
deadliest weather events in Texas history.

More counties in this state: Towns and villages in Texas.