This primary source comes from the Records of the Office of the Quartermaster General.
Full Citation: Water Color Drawing of Fort Pierre, Upper Missouri; ca. 1855; TR 12: Water Color - Fort Pierre Upper Missouri. (East Side View), 1855, 1794 - 1890; Consolidated Correspondence Files, 1794 - 1890; Records of the Office of the Quartermaster General, Record Group 92; National Archives Building, Washington, DC. [Online Version, https://www.docsteach.org/documents/document/water-color-drawing-of-fort-pierre-upper-missouri, May 30, 2023]