WEB5 days ago · San Antonio, city, seat (1837) of Bexar county, south-central Texas, U.S. It is situated at the headwaters of the San Antonio River on the Balcones Escarpment, about 80 miles (130 km) southwest of Austin. It is the second most-populous city in Texas. The Alamo, the city’s historic fort, is a popular tourist draw.