Our modern-day Halloween is a combination of several ancient festivals. The Celtic festival of Samhain (pronounced sow-in) is one such festival. This celebration happened on the last day of October after the harvest. It was intended to scare away ghosts over the long dark winter. People would dress up and dance around bonfires. Another such celebration is the Catholic festival of All Saints Day.
This was a time where people would dress up in costume and celebrate around fires as well. When America was settled many of these traditions were brought with the settlers of the southern colonies. Over time it has turned into the holiday we celebrate today with trick-or-treating and scary decorations.