Halloween originated in Great Britain and Ireland. It was derived from the name all hallows eve the Catholic holiday in celebration of all the saints.
The Irish introduced the tradition to America during the 1840's when many were fleeing their country to escape the potato famine.
The Irish also introduced America to the more superstitious folk lore surrounding Halloween as we know it today, that of witches and evil spirits.
To keep ghosts away from their houses on Halloween, people would place bowls of food outside their homes to appease the ghosts and prevent them from entering.
Halloween was a time for making mischief - many parts of England still recognise Halloween as Mischief Night - when children would knock on doors demanding a treat (Trick or Treat) and people would disguise themselves as witches, ghosts, kelpies and spunkies, in order to obtain food and money from nervous householders.