San Marcos, Texas map

San Marcos sits on I-35 exactly between the two big Central Texas cities: 30 miles south of Austin and 50 miles north of San Antonio. It is the seat of Hays County, whose 241,067 residents in 2020 were roughly double the 2000 count. San Marcos itself was named the fastest-growing city in the country among places over 50,000 for three consecutive years in the mid-2010s, and Hays County has stayed near the top of the national growth tables since.

The Balcones Escarpment runs through the western edge of the city. West of it, RM-12 climbs into the Hill Country toward Wimberley and Dripping Springs; east of it, SH-80 and SH-21 run out across flatter blackland toward Luling and Bastrop. Hays County borders Travis County to the northeast, Caldwell to the east, Guadalupe to the south, Comal to the southwest and Blanco to the northwest.

The springs surface under Spring Lake, a small impounded lake at the head of the river. The Meadows Center for Water and the Environment, run by Texas State University on the former Aquarena Springs resort site, operates glass-bottom boats over the spring vents; the lake is closed to swimming to protect endangered species that live nowhere else, including the Texas blind salamander and Texas wild rice.

Below the dam the San Marcos River runs through Sewell Park on campus, past City Park and Rio Vista Park, and out of town toward its confluence with the Guadalupe near Gonzales. The water holds close to a constant temperature year round, so tubing and swimming go on through the winter. Texas State University, founded in 1899 as Southwest Texas State Normal School, sits on the hill directly above the springs; Lyndon B. Johnson graduated from it in 1930, the only U.S. president to earn a degree from a Texas university. The university enrolls tens of thousands of students, which makes it by far the city's largest institution and the reason San Marcos has a much younger median age than either metro it sits between.

The other landmark on the interstate is commercial: two large outlet centres, San Marcos Premium Outlets and Tanger Outlets, face each other at the Centerpoint Road exit and pull shoppers from both Austin and San Antonio. Between them and the campus, I-35 through San Marcos carries some of the heaviest traffic on the corridor.