Tumacacori National Historical Park in the upper Santa Cruz River Valley of southern Arziona is comprised of the abandoned ruins of three ancient Spanish colonial missions. The Park is located on 45 acres in three separate units. San José de Tumacácori and Los Santos Ángeles de Guevavi, established in 1691, are the two oldest missions in Arizona. The third unit, San Cayetano de Calabazas, was established in 1756. Visitation to the Guevavi and Calabazas units is available only by reservation during monthly tours guided by the Park staff. All visitor services and Park operations are based out of the Tumacácori unit.