In the Appalachian foothills of western North Carolina, archaeologists have discovered remains of a 16th-century fort, the earliest one built by Europeans deep in the interior of what is now the United States. The fort is a reminder of a neglected period in colonial history, when Spain’s expansive ambitions ran high and wide, as yet unmatched by England.

If the Spanish had succeeded, Robin A. Beck Jr., a University of Michigan archaeologist on the discovery team, suggested, “Everything south of the Mason-Dixon line might have become part of Latin America.” But they failed.

Researchers had known from Spanish documents about the two expeditions led by Juan Pardo from the Atlantic coast from 1566 to 1568. A vast interior seemed open for the taking. This was almost 20 years before the failure of the English at Sir Walter Raleigh’s “lost colony” near the North Carolina coast or their later successes in Virginia at Jamestown in 1607 and at Plymouth Rock in 1620 — the “beginnings” emphasized in the standard colonial history taught in American schools.

One of Pardo’s first acts of possession, in early 1567, was building Fort San Juan in an Indian town almost 300 miles in the interior, near what is known today as the Great Smoky Mountains. It was the first and largest of six forts the expedition erected on a trail blazed through North and South Carolina and across the mountains into eastern Tennessee. At times Pardo was following in the footsteps of Hernando de Soto in the 1540s.