score:8
What I'm seeing there for good attestations are the following:
So it looks like the modern Jack-o'-lantern was a minor evolution from multiple very similar folk traditions already existing in the British Isles. The final evolution probably happened in North America, where all these traditions had a chance to intermix among the common settlers, along with a conveniently large native gourd. However, it didn't take very long for the entire activity (pumpkins excluded due to lack of availability) to be attested in the Scottish Highlands on Halloween, so the exact location can't be pinned with any certainty.