Four Spanish frontier missions, part of a colonization system that stretched across the Spanish Southwest in the 17th, 18th, 19th centuries, are preserved here. They include Missions San Jose, San Juan, Espada, and Concepcion. The park, containing many cultural sites along with some natural areas, was established in 1978. The park covers about 819 acres.

El Camino Real de Tierra Adentro is recognized throughout the United States of America and Los Estados Unidos de Mexico as a timeless route of trade and cultural exchange and interaction among Spaniards and other Europeans, American Indians, Mexicans, and Americans, which shaped individual lives and communities and affected settlement and development in the greater Southwest. Recognition of this route as an international historic trail will commemorate a shared cultural heritage and contribute in a meaningful way to eliminating cultural barriers and enriching the lives of people along El Camino Real de Tierra Adentro.

On May 8, 1846 troops of the United States and Mexico clashed on the prairie of Palo Alto in the first battle of a two-year war. Signed into law in June 1992, Palo Alto Battlefield National Historic Site located near Brownsville preserves the 3,400-acre scene of this clash between nations and informs visitors about its national and international importance. As the only unit of the National Park Service with a primary focus on the U.S.-Mexican War, Palo Alto Battlefield also interprets the entire conflict--including the details of its origins and the broad range of consequences. In an effort to turn a scene of conflict into a place of bi-national exchange and understanding, all research and interpretation conducted by the park reflects perspectives of both the United States and Mexico.