San Marcos is a city and the county seat of Hays County, Texas, United States. The city is a part of the Greater Austin Metropolitan Area. San Marcos's limits extend into Caldwell and Guadalupe counties, as well. San Marcos is on the Interstate 35 corridor between Austin and San Antonio. Its population was 44,894 at the 2010 census and 67,553 at the 2020 census.
