Izapa Stela 5: The Lehi Stone
This stone, currently possessed by The Smithsonian, was discovered in the ancient Mesoamerican city of Izapa, in 1941, by archaeologist Matthew W. Stirling. The stone carving has been dated to the Preclassic Guillen Phase between 300 BC and 50 AD. While both LDS and Non-LDS scholars debate the interpretation of the carving, it's hard to ignore the striking similarity it has to Lehi's dream of the "Tree of Life" found in 1 Nephi chapter 8. The tree of life, the people eating fruit, and other resemblances to the account of Lehi's dream, coupled with the location it was found, and it being dated dead on to the Book of Mormon timetable, makes this an intriguing evidence of Book of Mormon authenticity. But like all faith evidences, this won't make people believe who don't already.
The actual stone. Photo taken by Reed Fisher in 1965
A sketch of the carving. Notice the prominence of the tree, the father on the lower left offering fruit to his son, the river along the path. All prominent in the 1 Nephi 8 account.