Caithness is Clan Sinclair and Clan Gunn country. 

The Sinclairs are like the Stewarts, Gordons, Chisolms, Colquhons, Montgomerys and Frasers of Norman origin. They are believed to be descended from Rollo, or Rolf the Ganger, son of Rognvald the Mighty, Earl of Møre and Romsdal in Western Norway, and whose son became Jarl of Orkney (including Caithness). The Sinclairs first settled at Rosslyn, south of Edinburgh. By his father William’s marriage, Henry Sinclair became Jarl of Orkney, still a Norwegian title on 2nd August 1379. The Lairds of Caithness share a heritage with the Sinclairs and my family was given permission to wear the Sinclair Tartans (Red & Hunting) by the Clan Chief, the Rt Hon The Earl of Caithness PC. 
I also have a 4 x Grandparent, Sinclair McKay, born in Halkirk, Caithness.
The Ancient Green Tartan is the background to this site.
I created and maintained the Clan Chief’s web site www.clansinclair.org and handed it over in 2008.