South Texas Plains

South Texas Plains stretches from San Antonio south to the Rio Grande and west to the Mexican border, occupying the southern triangle of Texas. The landscape is mostly flat to gently rolling — mesquite brushland, scattered live oak mottes, and the broad agricultural valley along the Rio Grande. The climate stays warm, with the southernmost stretches frost-free most winters. Bexar County holds San Antonio and the urban anchor; Webb, Hidalgo, Cameron, and Maverick counties cover the river border; smaller counties like McMullen, La Salle, Frio, and Atascosa fill the brush country between. San Antonio, Laredo, McAllen, Brownsville, and Eagle Pass are the major cities, with smaller anchors at Castroville and Goliad. Trips here split by purpose. San Antonio handles the urban itinerary — the Alamo, the River Walk, the missions National Historical Park, the Pearl District. The Rio Grande Valley draws winter birders for South Texas specialties found nowhere else in the country. Most multi-day trips combine San Antonio with a side run to the Rio Grande Valley or Goliad’s mission and battlefield sites.