Complex sentence: He is most noted for his classic and oft-referenced 1882 book on the Army of the Cumberland, as well as his pioneering efforts to preserve and interpret the sites of the battles of Chickamauga and Chattanooga.
Split into simpler sentences: He is most noted for his classic and oft-referenced 1882 book "The Army of the Cumberland". In addition, Cist led pioneering efforts to preserve and interpret the sites of the battles of Chickamauga and Chattanooga.