BALTIMORE--There is a good reason why the Lincoln legend has taken on such mythical proportions: Much of what Americans think they know about Abraham Lincoln is in fact a myth. Let's consider a few of the more prominent ones. Myth #1: Lincoln invaded the South to free the slaves. Ending slavery and racial injustice is not why the North invaded. As Lincoln wrote to Horace Greeley on Aug. 22, 1862: "My paramount object in this struggle is to save the Union, and it is not either to save or destroy slavery. If I could save the Union without freeing any...