At Gettysburg is an autobiographical book of a teenage girl, Tillie Pierce, which recounted her experiences during the American Civil War. As a teenager, Tillie Pierce became well acquainted not just with the worries of war, but the horrors of military combat when a key battle of the American Civil War broke out in her hometown. When Tillie Pierce and her friends heard that Union troops were already on the move just after breakfast on the morning of July 1, 1863, they hurried off to watch the clash. In a really simple and easy way, a then 15 year-old, brings her view of the bloodiest battle of the American Civil War.