By 1531 Spain ruled present Mexico, Central America, the Caribbean, half of South America, and much of the United States, and the desire to claim new lands north of the Rio Grande led to continuous Spanish expeditions through present Texas during the 16th, 17th, and 18th centuries. The expedition of Alvar Nuñez Cabeza de Vaca traveled through Texas between 1526 and 1537, exploring and mapping the unknown territory. Later Spanish expeditions established missions, presidios, and townships, including those led by Alonso de Leon, Father Manuel de la Cruz, Father Juan LaRios and Fernando del Bosque, Domingo Teran de los Rios, and Father Isidro de Espinosa. At least twenty Spanish expeditions led by soldiers, missionaries, and settlers crossed present Medina County before 1844. Detailed descriptions of the area appear in the official accounts of many of the expeditions, and many of the county's geographical features retain the names given them by Spanish explorers of the 16th, 17th, and 18th centuries. Spanish names associated with early settlements, sites, rivers, and streams remain reminders of the area's rich Spanish heritage.