Located in the Franklin Mountains, extends west from Sadlerockit River along the south side of Ikiakpak Valley to the Canning River 15 miles southeast of Mount Copleston, Brooks Range.
Name applied by geologists in 1972. So named because "this range is the fourth and most southerly of a distinctive group of related mountain ranges. Each was carved from one of a series of four en echelon antielinal fold." (Board on Geographic Names (BGN) files).