John Alexander Logan (1826-1886) was an American soldier and political leader. He served in the Mexican-American War and was a general in the Union Army in the American Civil War. He served the state of Illinois as a Senator and was an unsuccessful candidate for Vice President of the United States. Logan was always a violent partisan, and was identified with the radical wing of the Republican Party. His forceful, passionate speaking, popular on the platform, was less effective in the halls of legislation. In 1868, he was one of the managers in the impeachment of President Andrew Johnson. Logan was the author of The Great Conspiracy: Its Origin and History (1886), a partisan account of the Civil War, and of The Volunteer Soldier of America (1887).