A relatively easy plateau summit near Granite Peak, usually climbed as a side trip once camped in the Sky Top Lakes basin.
Access is via the Lady of the Lake Trailhead off FSR 3230 near Cooke City. A trail follows Sky Top Creek to treeline and Lone Elk Lake, then continues past Rough Lake and into the Sky Top Lakes basin -- the same staging area used for Granite Peak's Southwest Couloir route. From a camp in the Sky Top Lakes basin, Cairn Mountain's west slopes are a walk-up of rocky tundra requiring only a few hours round trip, with the south face of Granite Peak dominating the view the entire way.