The Pennsylvania Hospital Unit was joined by medical personnel from St. Louis to form, as Norris wrote, the "first hospital unit in the whole U.S. to go overseas." They crossed the Atlantic on the Battleship St. Paul, which Norris described as "somber with guns ready."

During the transoceanic voyage the Pennsylvania Hospital Medical Unit had no idea that their European destination would be Le Tréport, France, a scenic town situated high on a cliff overlooking the English Channel. This contributed to the uneasiness that Norris described amongst the passengers.

On May 19, 1917, the Philadelphia staff of U.S. Base Hospital 10 left New York for "destination unknown."