Halloween originated from the ancient Celtic festival of Samhain, where the Celts believed the ghosts of the dead returned to earth on October 31st. People wore costumes to disguise themselves from these spirits. As Christianity spread, the holiday was transformed into All Saints' Day. The traditions of dressing in costumes and visiting homes for food or money evolved into modern-day trick-or-treating. The jack-o-lantern tradition originated from Irish immigrants carving turnips and brought the celebration to America. Today, Halloween is celebrated with costumes, parties, trick-or-treating, and eating candy.