I discovered the biggest, oldest Facebook group in February, 2020.

The name of the group is ATC Artist Trading Cards.

This group was established in 2012. The original admin of the group has not been active for years.  People come and go in ALL of the ATC groups, but this one remains the oldest.  Members of the other big ATC group call this group the Dragon Eye group.

My friend Emily Houtz got kicked out of the Dragon Eye group, and established the second main ATC group on February 8, 2024. She intentionally named her group with the same name as the older group: ATC Artist Trading Cards I usually refer to the group as "Emily's Group."

I no longer post on any Facebook group, but I do check in and read some of the interesting discussions that occur.