Twelve O'clock Knob is a mountain located in southwestern Roanoke County, Virginia, directly south of Salem, Virginia. According to local lore, slaves in the western Roanoke Valley noted that the Sun was directly over the mountain roughly around noon local time. In 1995 and 1996, the Tour Du Pont staged a time trial in the Roanoke Valley, the highlight of which was a ride over the steep, winding Twelve O'clock Knob Road.