This primary source comes from the Records of the Office of the Chief of Engineers.
Full Citation: The Approaches to the Tomb of the Unknown Soldier; 12/15/1930; Maps and Plans of Arlington National Cemetery, ca. 1913 - ca. 1965; 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/the-approaches-to-the-tomb-of-the-unknown-soldier, May 8, 2024]