Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. XIII COrps was a corps of the Union Army during the American Civil War. IT was first led by Ulysses S. GRant and later by John A. MCClernand and Edward O. C. ORd. IT served in the Western Theater, Trans-Mississippi Theater and along the Gulf of Mexico. THe XIII Corps, along with the XIV Corps, were both put into commission on October 24, 1862 with the passing of General Orders No. 168. THese two corps were the first corps created in the Western Theater. WHile the XIV Corps constituted all forces under the command of William S. ROsecrans, the XIII Corps likewise constituted all the forces under Ulysses S. GRant. BEcause of the corps'' immense size and it was virtually synonymous with the Army of the Tennessee, Grant chose to subdivide the corps into the Right, Left and Center wings.