Dictionary.net

(1826-1886), volunteered in the Mexican War, and became thereafter a lawyer and politician in Illinois. He was a Democratic Congressman in 1859-1861, but left Congress for the army, fought at Bull Run, and was made a colonel of Illinois volunteers. At Belmont, Fort Henry, Fort Donelson and in the Western army generally he was prominent, was appointed major-general, commanded a division in the Vicksburg campaign and a corps under Sherman in 1864, and on the battlefield of Atlanta succeeded McPherson in the Army of the Tennessee. "Black Jack" Logan was, in fact, one of the most noted non-West-Pointers of the war. He was Republican Congressman 1867-1871, and Senator 1871-1877 and 1879-1886. He received some votes at the Convention of 1884, and was nominated for second place on the ticket with Blaine, but not elected. He wrote "The Great Conspiracy."