SEGUIN, TEXAS. Seguin, the county seat of Guadalupe County, is on Interstate Highway 10 and the Guadalupe River, thirty-five miles northeast of San Antonio in the central part of the county. The land is suited for agriculture and ranching and is rich in oil and minerals. The Guadalupe River, the San Marcos River, and two major creeks, Cibolo and Geronimo, flow through the region. Archeological finds in the vicinity include the remains of mammoths east of Seguin and numerous Indian campsites along the Guadalupe River and various creeks in Guadalupe County. The first recorded evidence of exploration in the Seguin region was in 1718, when Martín de Alarcón, governor of the province of Texas, founded San Antonio de Béxar Presidio and San Antonio de Valero Mission in San Antonio and conducted several explorations north and east of San Antonio.