He was elected Attorney General of Wisconsin in 1859 and was the first Republican to hold that office. He was re-elected in 1861, but resigned office in October of 1862 to volunteer with the Union Army for service in the American Civil War. During his second term as Attorney General, Howe led the state delegation to recover the body of Governor Louis P. Harvey, who had drowned while on a visit to the wounded soldiers from the Battle of Shiloh.