Alexander Gardner’s Sketch Book documents the Civil War through photographs of military fortifications, hastily built bridges, Union soldiers at ease or in battle readiness, Confederate prisoners, and the dead. Of Timothy O’Sullivan’s pictures of the dead at Gettysburg, their shoes stripped off for the living and their pockets turned inside out, Gardner wrote, “It was, indeed, a ‘harvest of death.’ Such a picture conveys a useful moral: It shows the blank horror and reality of war, in opposition to its pageantry. Here are the dreadful details! Let them aid in preventing such another calamity falling upon the nation.”