William Taylor Adams (1822 – 1897), pseudonym Oliver Optic, was a famous academic, author, and a member of the Massachusetts House of Representatives. Adams in whole wrote over 100 books and most of them for a boy audience. «An Undivided Union» by Oliver Optic is the sixth and last volume of the «Blue and Gray — on Land» serious. Like its predecessors the book follows the adventures of the Riverlawn Cavalry, a Union regiment, raised in Kentucky, and participating in the daring campaigns undertaken by the Army of the Cumberland. As in the previous tales of this serious, Deck Lyon has again come to the front level as boldest hero, but his achievements all the time stay behind his foster brother. In this story the reader can overlook human principles of persons who are not wealing to yield each other.