Clan Gunn chieftains were powerful at an early stage. As well as holding substantial estates during the 13th-14th centuries, they also held the hereditary high office of Crowner (Crown Lord) of Caithness. But even during the time of Clan Gunn's greatest achievement, neighbouring clans, such as the Keiths and Sinclairs, were gaining estates through marriage. By the late 15th century Gunn strength was ebbing, estates were lost and there was a shift to the Highlands region of Caithness. By this time, chiefs of the clan had moved the clan seat a short distance to Halberry from Castle Gunn. It was here that George Gunn of Ulbster, Chief of the Clan and Crowner of Caithness resided. Two of the younger sons of George Gunn of Ulbster are claimed as the progenitors of the Hendersons, McWilliams, Williamsons, and Wilsons, of Caithness and Sutherland.