Williamson County, TX ZIP Codes & Directory
Complete postal guide for Williamson County, Texas. Featuring the official county seat of Georgetown, largest municipality Round Rock, and serving 4 incorporated municipal entities.
Municipalities Located in Williamson County
Incorporated Cities, Towns, and Villages
Active USPS Postal Codes in Williamson County
Standard delivery zones and geographic service boundaries
Frequently Asked Questions About Williamson County, TX
What is the county seat and largest city in Williamson County? ▾
The official county seat of Williamson County is Georgetown, and its largest incorporated municipality by population is Round Rock.
How many cities, towns, and villages are in Williamson County? ▾
Williamson County encompasses 4 incorporated municipal entities, including 4 cities, 0 towns, and 0 villages.
What is the total population and land area of Williamson County? ▾
According to official U.S. Census Bureau data, Williamson County has a population of approximately 609,017 residents and spans an area of 1,134 square miles.
How many postal codes operate in Williamson County? ▾
There are 4 active USPS postal codes serving addresses within Williamson County, Texas.