The Vinland Map, dated to about A.D. 1440--at least fifty years before Columbus landed in the Americas--is a unique map of the world that shows an outline of the northeast American coast and a legend describing its discovery in about 1000 by Leif Eiriksson, the Norseman from Greenland. The map was published by Yale University Press in 1965 and generated an enormous amount of debate. Chemical analysis of the ink later suggested the map might be a forgery,...