The three-day Battle of Gettysburg, Pa., in 1863 was the bloodiest clash of the Civil War, inflicting more than 50,000 casualties on the two sides. A natural spot, then, for postmortem sightings of the combatants? Several walking tours visit buildings where shades may dwell. The West Confederate Tour run by Ghosts of Gettysburg, for example, ambles down streets once briefly — or is it permanently? — occupied by Confederate soldiers. Seminary Ridge will give anyone spooky shivers, guided commentary or no. And at nearby Cashtown Inn or Farnsworth House Inn, it’s conjectured some late lamented guests never checked out.