Download the 436-page PDF file containing 16,700+ links (updated in January 2021) to genealogy & history Facebook groups/pages (in English) here: “Genealogy on Facebook” List
There is a clickable table of contents at the beginning of the list, starting with U.S. states & territories in the first section, other countries in the second section, and various categories in the third section (adoption, African American, Jewish, surnames, etc.). Clicking an entry in the table of contents will take you directly to that category within the list, and clicking a link will take you directly to that Facebook page/group.
Please note that, as of January 2021, all future updates and maintenance of the list is being handled by Cyndi Ingle of Cyndi’s List at https://cyndislist.com/facebook. Thank you, Cyndi!
Gail Dever has a broader Canadian list that includes French-speaking groups & pages that can be downloaded at Facebook for Canadian Genealogy, and Alona Tester has an Australian list that can be downloaded at Facebook for Australian History & Genealogy.