Montadale is a modern US breed developed in the 1930's in the mid-west from Cheviot rams with Columbia ewes. These sheep are raised for both meat and their exceptionally white wool which is in the "medium" range. Medium is right in the middle of all the types of wool and makes an excellent knitting yarn that is fairly soft but still fairly strong.
Farm source: hand selected fleeces from Saffer's Montadales in Warwick, Maryland on the Eastern Shore