Abe Lincoln's grandfather, Abraham, spelled his surname "Linkhorn." Was this because he was German (or of German descent)? Or because of the influence of his German neighbors in Virginia? Or because of a spelling error? In the early 1900s, Mr. Learned took on the task of thoroughly investigating the Lincoln family origins, "unearth ing] and exploit ing] much original matter relating to the Lincoln family in their American wanderings" through the states of Massachusetts, New Jersey, Pennsylvania, Maryland, Virginia, and Kentucky. Illustrated with copies of original documents. The Boone...