The Mexican War was one of the United States' shortest wars, and it's a conflict that often goes overlooked in American history books. But it was one that literally shaped the country and its future in so many ways. It added more than half a million square miles to the United States, from the Rio Grande to the Pacific Ocean, establishing a southern border and creating a territory that truly spread from sea to shining sea.  It was also where many future commanders of the American Civil War...