James Harrison Wilson (September 2, 1837 – February 23, 1925) was a United States Army topographic engineer and a Union Army Major General in the American Civil War. In the Maryland campaign, he served as an aide to McClellan, before joining Grant’s army in the West, where he was promoted brigadier. In 1864, he transferred from engineering to the cavalry, where he displayed notable leadership in many engagements of the Overland campaign, though his attempt to destroy Lee’s supply-line failed, when he was routed by a much-smaller and irregular Confederate force.