In 1540, the Spanish explorer García López de Cárdenas became the first European to see what?

García López de Cárdenas y Figueroa was a Spanish conquistador who was the first European to see the Grand Canyon.

López de Cárdenas was a conquistador attached to the exploits of Francisco Vázquez de Coronado. Expeditions, including one led by Pedro de Tobar, had heard reports of a large river north of Cíbola (Zuñi). Cárdenas was dispatched in September 1540 by the general stationed in Cíbola with the express mission of locating such a river and returning within 80 days. Pedro de Sotomayor accompanied him to record the event as a cronista. After some twenty days of marching in a northerly direction, he was successful; but his band found difficulties in reaching the river (called the River Tizon), owing to the sheer vertical distance down from their position. They were standing on the South Rim of the Grand Canyon. After several days of failed attempts to descend to the water (his men were suffering from thirst), his party was forced to return to Cíbola.