William Henry Jackson was an American photographer, Civil War veteran, painter, and explorer. He was most famous for his images of the American West. His photographic career began in 1869 when he won a commission from the Union Pacific to document the scenery along the various railroad routes for promotional purposes. His work was discovered by Ferdinand Hayden, who was organizing a geological survey to explore the Yellowstone River region. He asked Jackson to join the expedition as official photographer. He won numerous comissions from the US government and railroad companies, and built a large portfolio of photographs from around Colorado, the mountains, and American West.