This primary source comes from the Records of the Office of the Chief of Engineers.
Full Citation: Plan of Bedlow's and Ellis's Islands in the Harbour of New York; 8/7/1843; Drawer 113; 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://www.docsteach.org/documents/document/bedlow-and-ellis-islands, May 13, 2024]