Before the modern A90 road was constructed, the pass served as one of the eight major crossing points for those travelling over the Grampians to Deeside and into Northern Scotland; this entire crossing trackway is historically known as the Cairnamounth. C. Michael Hogan has noted that the alignment of the Cairnamounth trackway influenced ancient and medieval siting decisions for various castles, fortifications and other settlements in this region. Deriving from this theory, a small village grew up in the pass. The high granite tor of Clachnaben overlooks the road (now called the B974 road) through the pass. The Scottish Tourist Board describes the modern B974 as an "adventurous" road, and it is often impassable due to snow or flooding in winter. Despite this, it is said that the Clatterin' Brig restaurant on the south B974 ascent to Cairn O'Mounth is open all year round. In the summer fatalities are commonly reported in the press.
The presence of the mountain pass historically boosted the fortunes of the Howe o' the Mearns, a fertile area commanding the rough drovers roads known as the cairnamounth, approaching the Cairn O'Mounth pass from the south. Once over the top, on the northern side the road descends to the Bridge of Dye (or "Brig O' Dye"), and then proceeds to the drovers' favoured rest stop of Kincardine O'Neil village.
The Cairn O'Mounth pass was used by Edward I's English army in 1296 AD, en route back to England. The route over the pass is probably prehistoric: there is a cairn in the pass that has been dated to approximately 2000 BC. It is possible that this cairn is the one named in the name of Cairn O'Mounth.