At the 2010 census count, the city of San Marcos had a population of 44,894. Nearly a decade later, 64,776 people call San Marcos home, according to data released by the U.S. Census Bureau late May 20. This represents a 44% increase.

San Marcos is located in Hays County. The county, too, has seen substantial population growth since 2010. According to the census data released May 20, 230,191 resided in Hays County in 2019, up from 157,107 in 2010. This represents a 47% increase.