By a review of the documents and personal accounts of participants in the logistical system which supported the American Expeditionary Force in World War I, it is possible to trade the development of the system and to determine why changes were made. Entry into the war had caught the U.S. Army unprepared for war overseas. Its initial logistical system was based upon the pre-war Field Service Regulations. Once in France, it was necessary to modify these regulations in dealing with conditions overseas. Finally, in early 1918, the entire system was radically changed so that the American Expeditionary Force could be continuously supported. The story of this development is the subject of this thesis.