There is an often-repeated 'fact' that although the pumpkin is an American plant, the Jack-o-Lantern tradition is an older Irish tradition (e.g., in today's Washington Post) in which turnips were carved rather than pumpkins.
I was surprised that the Wikipedia article seems to treat this as a popular myth! While it recognizes that there are old reports (and museum specimens) of carved turnips (mid 1800s), it seems that there is even older evidence of carven pumpkins in the Americas (early 1800s, cf. Legend of Sleepy Hollow).
These are relatively recent dates and it seems like there should be lots of written records! So is the Halloween tradition of carving a face into a vegetable and illuminating it from within by a candle something that went from Ireland to America, or America to Ireland?