In the 18th century, Spanish priests established five Catholic missions along the San Antonio River. Today, the five missions (Mission San Antonio de Valero, Mission San José, Mission Concepción, Mission San Juan and Mission Espada) represent the largest concentration of Spanish colonial missions in North America and have been named a World Heritage Site by the United Nations Educational, Scientific and Cultural Organization (UNESCO).

UNESCO encourages the identification, protection and preservation of cultural and national heritage around the world. To be chosen as a World Heritage Site, the missions had to meet demanding selection criteria. This rare honor has been bestowed upon only 24 sites in the United States. The missions are the first and only World Heritage Site in Texas.