This is the updated list of rare sheep breeds, combining those listed by The Livestock Conservancy (U.S.) and the Rare Breeds Survival Trust (U.K.).
If you’re interested in watching the shifts in breed status, I have been developing spreadsheets tracking listings of rare breeds of sheep by The Livestock Conservancy (under its current and previous names: the American Minor Breeds Conservancy and the America Livestock Breeds Conservancy) and the Rare Breeds Survival Trust. For the former, I’ve collected information (so far) from 1989 to 2018. For the latter, I only have 2012 to 2018. I’ve dug through back issues of the RBST’s The Ark, but the lists have only been published there in recent years and I haven’t been able to find them archived on the web.
Note that these spreadsheets are working documents, and thus not pretty, but they may be interesting to others.
The Livestock Conservancy’s data:
The Rare Breeds Survival Trust’s data (as far as I’ve been able to collect it so far):
(For those who might be interested, I have summaries of the other livestock being tracked by The Livestock Conservancy in its current and previous incarnations. I have not kept those as closely up-to-date as I have the sheep information; mammals much more thoroughly tracked than poultry, although I have some data on the birds as well.)