high knob stretches across portions of southern wise county, northern scott county, and the northeastern tip of lee county. it is a significant physical features in virginia and is among the widest singular mountains in the southern appalachians, being locally greater than 13 miles ( 21 km ) wide from base to base and more than 26 miles (42 km) long. it represents the "pivot point" of the cumberland mountain overthrust block. (first described in notable detail during the 1920s and 1930s by geologists charles butts and john rich).