In WWII, children were evacuated usually by train or boat.
If it was by boat then that usually meant that they were being migrated to Canada to keep safe from the bombing in Britain. However, immigration was strict and not popular in the USA. at the time. At least one boat got sunk from German torpedoes on it's journey.
If it was by train, that usually meant being shipped to the countryside to keep safe as there were not many bombings in the countryside during WWII.