The refugees were aboard the MS St. Louis, a German ocean liner turned away by Cuba and the United States in 1939.
The St. Louis sailed from Hamburg on May 13, 1939, carrying 937 passengers, most of them Jewish refugees fleeing Nazi persecution. The ship reached Havana later that month, but Cuban authorities allowed only a small number of passengers to disembark after recently changing the country's entry rules. The remaining passengers hoped the United States would admit them, but American officials also refused permission to land.
Captain Gustav Schröder eventually had to return the ship to Europe. Countries including the United Kingdom, Belgium, France, and the Netherlands agreed to accept groups of passengers. The episode became known as the “Voyage of the Damned.” The common short answer “St. Louis” is the ship's identifying name; its formal designation is often written as MS St. Louis.