This primary source comes from the Records of the Office of the Chief of Engineers.
Full Citation: United States Air Service 32-Hour Transcontinental Flight New York to San Francisco; 1919; United States; War Department Map Collection, 1939 - 1942; 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/united-states-air-service-32hour-transcontinental-flight-new-york-to-san-francisco, May 13, 2024]