According to The Blackface Sheep Breeders Association (UK):
Scottish Blackface Sheep History
The breed’s origin is lost in the midst of time, but undoubtedly emerged from the genetic umbrella of’ horned sheep from which also sprung the Swaledale, Rough Fell and other localised types such as the Lewis and Mayo Blackface.
Monastery records of the 12th century tell of the Dun or Blackface breed of sheep. The monks used the wool for their clothes, and also exported large amounts to Europe.
In the 16th century, King James IV of Scotland established an improved Blackface flock in Ettrick Forest. During the 17th and 18th centuries. It was known as the Linton Sheep, West Linton in Peeblesshire being the main sale for the type.
In the early 19th century, the breed was taken from Dumfriesshire and Lanarkshire and introduced into the north of Scotland, but due to the high price of cheviot wool the Blackfaces were cleared off the hills in favour of the cheviot. This continued until 1860, when the wool prices reached the same level and the farmers realised that the blackface, with its ability to survive and reproduce in adverse weather conditions, was the best suited breed to utilise hill and mountain grazing.
In the late 19th century, there was an upsurge in interest in breed improvement. Many of the farms that sold high priced tups and enthusiastically promoted the breed at that time possessed names that are still well known today.