Located on what is today New Jersey soil, the hospital facilities on Ellis Island, run by the Public Health Service (PHS) to treat immigrant patients, were a medical marvel of their time. While known primarily for its use as an immigration facility, Ellis Island went through several major changes from the time war was declared in Europe in 1914, to the time that the last military members left the Island in 1919. During the First World War, Ellis Island and its associated hospital facilities would be the victims of German terrorism, a mobilization point for thousands of Red Cross nurses bound for the frontlines, and a debarkation hospital that was the first stop home for countless sick and wounded soldiers returning from the battlefield. This paper examines how the PHS, the Red Cross, and the Army Medical Corps tried to protect public health, screen immigrants for disease, and care for our military casualties, all under the tension and strain of a world war and a global pandemic.