This primary source comes from the Records of the Office of the Chief of Engineers.
National Archives Identifier:
305713Full Citation: Topographical Map of Fort Donelson, Tenn., and Vicinity. Prepared under the direction of Col. Wm. E. Merrill, 1st U.S.V.V. Eng'rs., Chief Engineer, Dept. of the Cumberland, By Maj. James R. Willett, 1; 1/1865; Records of the Office of the Chief of Engineers, Record Group 77. [Online Version, https://www.docsteach.org/documents/document/topographical-map-of-fort-donelson-tenn-and-vicinity-prepared-under-the-direction-of-col-wm-e-merrill-1st-usvv-engrs-chief-engineer-dept-of-the-cumberland-by-maj-james-r-willett-1st-usvv-engrs-chief-i, May 3, 2024]