Photographer Timothy H. O'Sullivan, widely known for his images of Civil War battlefields and the Western United States, began his photography career as an apprentice to Mathew Brady. When the Civil War broke out 1861, he was commissioned a first lieutenant in the Union Army and, over the next year, fought in (and photographed) battles at Beaufort, Port Royal, Fort Walker, and Fort Pulaski. After joining Alexander Gardner’s studio, O'Sullivan published 44 photographs in the first published collection of Civil War photographs, Gardner's Photographic Sketch Book of the War. His most famous photograph is The Harvest of Death (1863), which depicts dead soldiers strewn on the battlefield at Gettysburg. From 1867 to 1869, O’Sullivan was the official photographer on the United States Geological Exploration of the Fortieth Parallel, where he created photographs to attract settlers to the West.