What is the Mystery of the first Americans?

Answer 1

The first Americans were the natives that lived on this land when the europeans landed. Are you talking about the colonists at Roanoke?

http://www.nationalcenter.org/ColonyofRoanoke.HTML

"This Colony was run by Ralph Lane after Sir Richard Grenville, who had transported the colonists to Virginia, returned to Britain for supplies. These colonists were ill-prepared and not particularly clever, because, although they depended upon the local Indians for food, they also antagonized the Indians by such tactics as kidnapping them and holding them hostage in exchange for information. Unfortunately for the colonists, who were desperately in need of supplies, Grenville's return was delayed. As a result, when Sir Francis Drake put in at Roanoke after destroying the Spanish colony of St. Augustine, the entire colony returned with Drake to England.

"Interestingly, when Drake picked up these colonists, he left behind 15 of his own men, who were never heard from again. This foreshadowed one of the great mysteries of North America, Roanoke's so-called "Lost Colony" of 90 men, 17 women and 9 children, founded in 1587 and discovered to be missing in 1590, but for the word "Croatan" carved on a post. Although both the English and the Spanish searched for clues to the colony's disappearance for many years, the mystery has never been solved."