This primary source comes from the Records of the Office of the Chief Signal Officer.
National Archives Identifier:
531019Full Citation: Troop L, 6th U.S. Cavalry, at the Great Wall of China, near the Ming Tombs. East of Nan-Kow Pass; 1900; Records of the Office of the Chief Signal Officer, Record Group 111. [Online Version, https://www.docsteach.org/documents/document/troop-l-6th-us-cavalry-at-the-great-wall-of-china-near-the-ming-tombs-east-of-nankow-pass, May 2, 2024]