Wikipedia
Moncacht-Apé was a Native American explorer of the Yazoo tribe in the present-day Mississippi area; in the early 1700s he may have made the first recorded round trip transcontinental journey across North America.
Some years after his purported journey from the Atlantic to the Pacific, Moncacht-Apé related his adventures and itinerary to Antoine-Simon Le Page du Pratz, a French explorer and ethnographer in the colony of Louisiana. Le Page published his memoir in the 1750's, including material from Moncacht-Apé's account. He said that native people on the West Coast had told him of their ancients coming to North America by a land bridge.
A partial English translation of Le Page's book was published in 1763. As it included material about the peoples and the geography of greater Louisiana, it was taken as a guide by later European and American pioneers, including Lewis and Clark, during the continuing exploration of North America.
Some historians have disputed the fact of Moncacht-Apé's transcontinental journey. Le Page's is the only first-hand account of Moncacht-Apé's story, and its veracity is difficult to confirm.