Halloween originated 2000 years ago among Celtic pagans in Ireland, England, and France. They celebrated Samhain on October 31st, when spirits of the dead were believed to return to Earth. People wore costumes to avoid recognition by ghosts. As Christianity spread, the holiday was changed to All Saints' Day on November 1st. Trick-or-treating began as poor people begging for soul cakes in return for prayers. Irish immigrants brought Halloween traditions to America in the 1800s, carving pumpkins instead of turnips and celebrating with costumes and candy.