Why was there a jack-o-latern on Halloween?

Answer 1

There has been a long tradition of carved vegetables in the British Isles. When immigrants came to the U.S., the pumpkin was much more readily available and was easier to carve than the traditional turnips. They were associated with the harvest (since that is when they would ripen) and slowly became associated with Halloween (possibly because the origin of the name tells a tale of a man who associated with the devil and Halloween is supposed to be a day when devils, demons, witches, and the like are out).