Austin,_Texas | isPartOf | Hays_County,_Texas Williamson_County,_Texas | largestCity | Round_Rock,_Texas Austin,_Texas | isPartOf | Williamson_County,_Texas Williamson_County,_Texas | countySeat | Georgetown,_Texas
Round Rock is the largest city in Williamson County, Texas, while the county seat is Georgetown. Austin is also part of Williamson County and is additionally partly located in Hays County, Texas.