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, of which Austin is a part of, in Texas. Austin is also part of Hays County in Texas. Georgetown is the county seat of Williamson County, Texas.