San Marcos has been a crossroads since before Texas was a state

People used San Marcos Springs at least 8,000 years ago. Anglo-American settlers arrived in 1846. By 1848, San Marcos became the county seat. The International-Great Northern Railroad came in 1880. By 1890, the town had about 2,300 residents.

Southwest Texas State Normal School (now Texas State University) opened in 1903. It became one of the biggest employers in the area. The city had about 9,980 people in 1950. By 2020, that number had grown to more than 67,000. Today San Marcos has the county government, the university, and a large retail strip along IH-35.