The County of Mortain was a medieval county in France centered on the town of Mortain. A choice landholding, usually either kept within the family of the Duke (or the King in some cases), or more often it was granted to a Lord in return for royal service and favor. This was the main reason Mortain had so many Counts, as shown below, during its long history.
^Einhard: The Life of Charlemagne (trans. & pub. by Harper Brothers, 1880)
^ There are apparently few certain facts about William Warlenc, who was deprived of the County to the benefit of Robert (sometimes said to have been c.1055).