The following is a highly abbreviated summary of the history of the Robertson clan (and other information) at www.robertson.org. For further information please contact the owners of that site.
The Scottish clan Robertson derives from Donnachaidh, or 'children of Duncan'. According to the website above, the Romans called this tribe the kaledonioi, one of the eleven tribes of the northern Pictish nation, living in the area now known as Atholl, in Perthshire.
The website also notes the history of Duncan, who became King Duncan I in 1034. King Duncan was defeated by his first cousin MacBeth in battle in 1040. Duncan's son Malcolm then killed MacBeth in 1057 and became King Malcolm III Ceann Mor (Canmore). After his death in 1057, Malcolm's son Duncan became King Duncan II but was then murdered by his uncle. Duncan II's brother Edgar became king in 1097.
After the death of Alexander III, the last male member of the family, in 1286, the clan had no chief for almost 30 years when Donnachadh Reamhair, or "Stout Duncan" took over. Stout Duncan had four sons: Robert, Patrick, Thomas and Gibbon. Robert became the second Chief in 1355 and died sometime after 1392. Robert's eldest son Duncan was the third Chief.
Duncan's eldest son, Robert Ruabh Duncanson, was the fourth Chief. His sons became known as Robert's sons, or Robertson and they lived in Struan.
The Robertson clan area was primarily located in the south-eastern highlands around Straun, approximately 100 kilometres north west of Dundee and north east of the northern end of Loch Tay. This map from www.robertson.org explains the main areas of interest.
Other prominent names in the area were Farquharson, Ogilvy, Macintosh, Macthomas, Stewart, Spalding. For a map of all Scottish clans, see this map from Wikipedia.:
Page created 31 December 2011, updated 18 March 2017. Copyright Andrew Warland.