Which Spanish explorer founded present-day Texas, Oklahoma, New Mexico, and Arizona?

The choice of Francisco Vázquez de Coronado is correct because he led an expedition in the 1540s that explored large parts of what is now the southwestern United States, including present-day Texas, Oklahoma, New Mexico, and Arizona. Coronado embarked on this journey in search of the legendary Seven Cities of Gold but instead documented the diverse landscapes and indigenous cultures of the region. His explorations were significant in expanding Spanish knowledge of North America and laid the groundwork for future Spanish settlement.

Other explorers listed did not establish the territories specified in the question. For instance, Juan Ponce de Leon is primarily known for his explorations in Florida, especially his search for the Fountain of Youth. Hernando Cortes is famous for the conquest of the Aztec Empire in Mexico. Christopher Columbus is credited with opening up the Americas to European exploration but did not venture into the lands that would become Texas, Oklahoma, New Mexico, or Arizona. Each of these figures played important roles in Spanish exploration, but it was Coronado's expedition that specifically focused on the southwestern U.S. regions mentioned.