Caddo Mounds State Historic Site, near Alto in East Texas, preserves the remains of the southwesternmost ceremonial center built by the Caddo, or Hasinai, people, part of the broader Mound Builder tradition of prehistoric North America. Occupied from roughly A.D. 850 to 1300, the site originally functioned as a major civic, religious, and political center for a hierarchical Caddo community: earthen mounds served as platforms for temples and elite residences and as burial grounds for high-status leaders, while the surrounding village supported farming, craft production, and trade across a wide region of the southeastern woodlands. The complex reflects the Caddo's sophisticated social organization, with mound-building activity tied to ceremonial and political authority rather than everyday domestic use. The community was gradually abandoned by the fourteenth century, well before European contact, and the mounds themselves survived largely intact into the modern era. Today the site no longer serves any original ceremonial purpose; instead it is preserved and interpreted by the Texas Historical Commission as a state historic site and archaeological museum. Visitors can walk a self-guided trail past the surviving mounds, view a reconstructed Caddo grass house built using traditional methods, and explore a visitor center with exhibits on Caddo history and culture, making the site primarily an educational and archaeological preservation landmark rather than a place of continuing habitation or ritual use.