James Harrison Wilson (1837-1925) was a U. S. Army topographic engineer, a Union Army general in the American Civil War and later wars, a railroad executive, and author. After the start of the Civil War, he became the topographical engineer for the Port Royal Expeditionary Force. In 1864, Wilson switched from engineering to the cavalry. In 1864, he was assigned as chief of the Cavalry Bureau in Washington, D.C. He was an excellent administrator and organizer, but his true talents turned out to be as a combat leader. At the end of the war, Wilson reverted to the rank of lieutenant colonel and was assigned to the 35th U. S. Infantry, but his duty assignments continued to be in the Corps of Engineers until he resigned from the Army in December 1870. After he left the Army, Wilson worked as a railroad construction engineer and executive. For the next 15 years he devoted his time to business, travel, and public affairs, and wrote on a number of subjects. He returned to the Army in 1898 for the Spanish-American War and retired from the Army in 1902.