The establishment of a legal basis for a foreign hospital in Paris and the raising of funds to make it happen was a slow process lasting from 1904 to early 1910. The American Hospital of Paris---not actually located in Paris, but in the western suburb of Neuilly-sur-Seine---also had a legal existence in the United States, incorporated in the State of New York.
The ruling authority for the Hospital was its Board of Governors. The hospital director was appointed by and answered to this board.
The American Hospital would be the legal and administrative vehicle through which the temporary wartime activities of its offshoot, the Ambulance (and its Field Service), could take place.
A few words about the hospital's background: In 1910 Mr. J. Harjes, Sr., a co-founder of the Bank of Morgan, Dr. Mangin, a leading American physician, and a number of other influential Americans proposed the establishment of a hospital in Paris to meet the needs of the growing American colony. In 1913, a year before the beginning of the First World War, this group induced the United States Congress to grant a charter for it. At the outbreak of the conflict, Myron C. Herrick, our ambassador to France, proposed that the American Hospital be transformed into a military medical base to serve the Allied armies. The French Government turned over to the Americans the Pasteur High School building in Neuilly (which was larger than the original establishment). Donations came in from the United States, and outstanding American doctors --- Blake, Cushing, Crile --- offered their services. The hospital was the first medical institution in France to incorporate a dental department, whose restoration of the jaws of wounded soldiers was a pioneer achievement in plastic surgery.
When the German Army of von Kluck bore down on Paris in the fall of 1914, the hospital purchased a fleet of Ford chassis, mounted ambulance bodies on them, and transported the wounded from the front. According to Ambassador Herrick's testimony, there were no more useful ambulances at the front than these Fords, which could penetrate practically anywhere. Indeed, the story of American Hospital ambulances is as stirring in its fashion as the saga of General Gallieni's emergency taxis which rushed reinforcements to save the Allies at the Marne.
The American Hospital became famous among the soldiers. British tommies and French poilus went into battle with messages in their pockets begging to be sent there if they were hit. People from every walk of life did volunteer work in its wards. Dr. George Crile, who joined the staff, writes that one orderly in his operating room was a grand-opera singer, another was a portrait painter, and still another was a member of a well-known banking firm. Mrs. W. K. Vanderbilt worked as a nurse.
Dr. Charles F. Bove with Dana Lee Thomas. A Paris Surgeon's Story. Boston: Little, Brown. 1956, pp 29-30.
Nicole Fouché, Le mouvement perpétuel, histoire de l'Hôpital américain de Paris 1906-1989, Toulouse: Erès, 1992