This study analyzes the procedures and operations of the Quartermaster, Ordnance, Commissary, and Medical Departments during Scott's campaign to determine the efficiency of the prevailing logistical system. Unpublished and published government documents, official records, manuscript collections, memoirs, diaries, and newspapers provide the data. The first chapter describes the logistical departments interworkings; the remaining chapters detail the operations of the bureaus during the expedition's assembly and campaign against Mexico City. The evidence revealed organizational deficiencies which caused severe shortages, particularly in transportation, for Scott's army. The shortages severely hampered the expedition. Because of .the numerous victories over 'Mexican forces, however,. American leaders ignored the organizational deficiencies, These shortcomings reappeared to .impede operations during the Civil War.