Santa Maria del Rio is one of the 58 municipalities that make up the Mexican state of San Luis Potosí.
The municipality is located in the southern part of the state, approximately 48 kilometers east of the city of San Luis Potosí.
Santa Maria del Rio is located in the center of the southern part of the San Luis Potosí, at an average altitude of 1,710 meters above sea level.
Santa Maria del Rio lies on the Mexican Mesa del Centro on the western edge of the Sierra Madre Oriental[2] and consequently has a mountainous terrain, with various hills: the Membrillo, the Rincón Pilitas, the Duraznillo, San Pablo, the Platanito, San Antonio, the Banqueta, the Pachona, the Joya, the Mesa Prieta, the Barbechos, as well as the Sierra de Bagres.
Because of its elevation, Santa Maria del Rio has a dry, temperate climate, cooler in the highlands and warmer in the lowlands.
Archaeological evidence shows that the region was once occupied by people of advanced culture, sedentary farmers who built permanent structures.
In May 1914, the town of Santa Maria del Rio was the site for fierce fighting between the 150 occupying huertistas and the Constitutionalists.