Great! I was also wondering whether anyone on your team has more data about what towns were part of America/Nipigon. I'm trying to map all of the Canadian IANA zones on OpenStreetMap. Your tzdb mentions that Nipigon was the largest town in its zone, which suggests that the zone wasn't limited to Nipigon town boundaries, but it doesn't give any clues about what other towns were found to follow it. Thanks in advance.