This primary source comes from the Records of the Office of the Chief of Engineers.
Full Citation: Plan of the City of Mexico and its Defences, September 13th 1847, upon the Approach of the American Army under Major Genl Scott; 6/29/1848; Drawer 112; Fortifications Map File Plans of Military Forts, 1818 - 1941; Records of the Office of the Chief of Engineers, Record Group 77; National Archives at College Park, College Park, MD. [Online Version, https://docsteach.org/documents/document/city-of-mexico-and-its-defences, May 19, 2024]