In 1513 exploration of the interior of the two continents began.
Balboa crossed the Isthmus of Panama, 1513, and Cortes conquered Mexico, 1519-21.
3.

In 1528 Narvaez made the first serious attempt to enter the Mississippi valley.

He died, and some of his followers, under Cabeza de Vaca, crossed the continent.
4.

When the Spanish governor of Mexico heard their story, he sent Fray Marcos to find the "Seven Cities of Cibola"; and began the exploration of the southwestern part of the United States.
5.

In 1539-1541 De Soto and his band explored the southeastern part of the United States from Florida to the Mississippi River.
6.