Thomas Moran was an Anglo-American landscape painter and a key representative of the Hudson River School and the Rocky Mountain School. His most famous works were created after his participation in the geological expedition to Yellowstone National Park in 1871. The paintings that Moran created from this experience convinced the US Congress of the need to protect Yellowstone as the world's first national park. Moran thus became not only a pioneer of landscape painting, but also a forerunner of the conservation movement.