The Celts that lived in what is now Great Britain and Northern France would carry a lantern when they walked on the eve of October 31. These lanterns were carved out of big turnips and the lights were believed to keep the evil spirits away. Children would carve faces in the turnips. These carved turnips were called "jack-o-lanterns.
Legends have it that the "jack-o-lantern" got its name from a stingy and mean old man, named Jack, who when he died was too mean to get into heaven. When Jack went to hell he was meet by the Devil who gave him a piece of burning coal and sent him away. Jack placed the burning coal in a turnip to use as a lantern to light his way. The legends claim that Jack is still walking with the lantern looking for a place to stay.
When the early settlers came to America they found the big round orange pumpkin. Being larger and much more colorful than turnips, the pumpkin made great "jack-o-lanterns". Eventually the pumpkin would replace the turnip.
As the settlers spread across America they took their Halloween celebrations with them. The custom of the "jack-o-lantern" would travel with them. Eventually the Pumpkin would become the most widely recognized symbol of the Halloween holiday.