They initiated the Samhain, which then changed into All Saints' Day, once the Roman conquered them. Their disguises in ghosts and witches became a real ritual for the Romans who strongly believed that they could be possessed by evil spirits. This celebration was dedicated to the spirits of the dead, these being considered to wander the Earth in search for a way to get to the other side and live their afterlife. They celebrated this Samhain festival on the 31st of October, at the same time as New Year's Eve.

They also dressed in frightening costumes and wandered around the village, trying to be as scary as possible in order to chase the ghosts and the spirits away from the village. This way, their houses became unattractive for the dead and no spirit wanted to stop by. Once they were conquered by the Romans, the Celts transmitted some of their traditions to the Romans, too. Of course, the living didn't want to be possessed, so that everyone turned their lights off on the 31st of October. Halloween appeared a few thousand years ago in the Celtic culture.

Halloween was brought to America by the Irish immigrants who.