Old Lyme resident here, high school class of 82 - it was the younger siblings of my classmates who were getting "Lyme arthritis" starting in the late 70s or maybe 1980.

Like most of the populated Northeast, most the area was cleared farmland or grazing land until WWI or maybe WWII - all those stone walls in the middle of the woods used to be borders between open fields. I don't think there was an ecosystem that could support Lyme disease near where people lived until maybe the 70s - the cycle needs both deer and mice, in proximity to humans to get infected, and you're not going to get either of them on open land that's grazed or under cultivation.

So Lyme disease could have been around long before that, farther into the woods, and probably wouldn't have been noticed by people who had good enough doctors to figure out what was going on, or were healthy (rich?) enough for the symptoms of Lyme disease to be considered something out of the ordinary.

The fact that Lyme disease exists in Europe already seemed to indicate that it's been around a very long time, but this finding adds more evidence. For that matter, I wonder if it's yet another disease that was introduced to the Americas by Europeans?