Williamson County Texas map
30.65° N · 97.61° W · County seat: Georgetown · 1,132 sq mi · Central Time
Williamson County grew from 609,017 people in 2020 to an estimated 727,480 in 2024, one of the sharpest rises of any county in the United States. Almost all of that happened along a 25-mile stretch of I-35 between Round Rock and Jarrell, where the suburbs of Austin meet farmland that was growing cotton and sorghum a generation ago.
Centered near Georgetown. I-35 runs top to bottom through the middle; the two arms of the San Gabriel River meet just east of the Georgetown square.
Where Williamson County sits
The county is directly north of Austin. Bell County borders it on the north and Milam County on the northeast. Bastrop and Lee counties touch the southeastern corner, Travis County forms the southern line, and Burnet County is the western neighbor.
The Balcones Escarpment runs north to south through the middle of the county, roughly along the line from Jarrell through Georgetown to Round Rock — which is also roughly the line of I-35. West of it the land is hilly limestone country on the eastern fringe of the Hill Country, with live oak, cactus and caves. East of it the ground is flat to gently rolling with deep dark clay, the soil that made Taylor and Granger farm towns.
Straight-line distances from the county's center point: Georgetown 4 miles, Round Rock 11 miles, Austin 28 miles south, Killeen 33 miles north and Temple 35 miles northeast.
Williamson County was cut out of Milam County in 1848 and named for Robert McAlpin Williamson, a Republic of Texas judge and San Jacinto veteran known as Three-Legged Willie because a leg fused at the knee left him walking on a wooden peg.
Cities and towns
| Place | Type | 2020 population in county |
|---|---|---|
| Round Rock (part) | City | 117,612 |
| Cedar Park (part) | City | 70,097 |
| Georgetown | City (seat) | 67,423 |
| Austin (part) | City | 60,333 |
| Leander (part) | City | 50,057 |
| Hutto | City | 27,586 |
| Taylor | City | 16,297 |
| Liberty Hill | City | 3,568 |
| Jarrell | City | 1,760 |
| Granger | City | 1,179 |
| Florence | City | 1,174 |
| Bartlett (part) | City | 939 |
| Thrall | City | 815 |
| Weir | City | 698 |
Several of these towns have grown steeply since 2020: Liberty Hill and Jarrell more than tripled in the 2024 estimates.
Roads and toll roads
- I-35 – enters from Bell County above Jarrell and runs south through Georgetown and Round Rock into Travis County.
- SH-130 – the tolled bypass east of I-35, beginning near Georgetown and heading southeast past Hutto toward Travis County.
- SH-45 – two separate tolled segments, one linking SH-130 to US-183 on the north side of Round Rock, one on the southwest county line.
- US-183 and the 183A toll road – northwest through Cedar Park, Leander and Liberty Hill; 183A is the tolled parallel lane through the Leander corridor.
- SH-29 – the main east–west route, running from Burnet County through Georgetown to Granger and the Milam County line.
- US-79 – northeast out of Round Rock through Hutto and Taylor toward Milam County and Rockdale.
- SH-95 – a north–south farm route through Taylor and Bartlett, well east of I-35.
The San Gabriel River and its reservoirs
Three forks of the San Gabriel River drain the county. The North Fork and South Fork come off the escarpment separately and join at Georgetown; the Middle Fork feeds the North. Lake Georgetown, a Corps of Engineers reservoir, sits on the North Fork just above the city and supplies most of the county's municipal water. Downstream, past Circleville, Granger Lake impounds the main stem of the San Gabriel near the town of Granger on the flat eastern side. Below that the river runs on into Milam County to meet the Little River.
The same limestone that carries the river is riddled with caves. Inner Space Cavern opened beside I-35 south of Georgetown after a highway drilling crew broke through the roof of it in 1963 while taking core samples for the freeway.
Campuses and employers
Southwestern University, a small private liberal arts college, sits a few blocks northeast of the Georgetown courthouse square. Dell has its headquarters campus in Round Rock, which is the single largest reason Round Rock grew from a highway town into a city of more than 100,000. On the eastern side of the county, Samsung is building a semiconductor fabrication complex at Taylor, a project that has pulled housing and supplier construction out along US-79 and SH-95.
Georgetown's courthouse square is a National Register historic district, and the county's older east-side towns — Granger, Thrall, Bartlett and Walburg — were settled heavily by Czech and German farming families whose churches and halls still mark the crossroads.