The Marc Lagen World War I Collection contains military documents, photographs, correspondence, and ephemera relating to the military service of Captain Marc Aloysius Lagen in the Balloon Section of the U.S. Air Service during the war. The collection is organized into two series: photographs and textual materials.

Photographs include many aerial reconnaissance images taken by both French and American airmen, as well as portraits and candid views of soldiers and officers in France, aircraft, and war ruins. Other materials include a number of documents related to post-war issues including the return of supplies and a claim for lost property from a barracks fire, a notebook from Lagen's training, some personal correspondence, financial records, and ephemera. Please note that some of the items in Box One, Folders 3 and 5 contain graphic images of wartime casualties.

In series II, a substantial number of military orders, memos, and other communications trace Lagen's travels and transitions from the National Guard and a brief stint on the Mexican border to his commission with the Signal Corps and assignment to the front in France. The papers reflect Lagen's simultaneous work with the French and American militaries.