After the outbreak of the Civil War, John joined the Union Army and held the rank of Lieutenant in the 20th Illinois Infantry. In 1862 he fought along with Generals Grant and Sherman at the battle of Shiloh where he lost his right arm. In 1869 he led a nine-man expedition on the first full-length exploration of the Colorado River, including exploration of the Grand Canyon. In 1871 Powell led another expedition that again led him to the Grand Canyon. Powell was a professor of geology at Illinois Wesleyan University and helped to found the U.S. Geological Survey. He was the organization's director from 1881 to 1894.