Austin,_Texas | isPartOf | Hays_County,_Texas Hays_County,_Texas | largestCity | San_Marcos,_Texas Austin,_Texas | isPartOf | Williamson_County,_Texas Williamson_County,_Texas | countySeat | Georgetown,_Texas
Austin, Texas, is part of Hays County, Texas, the largest city of which is San Marcos. Austin is part of Williamson County, of which Georgetown is the county seat.