(3) the Blue Ridge and Valleys--Although the Blue Ridge Mountains are a part of the Appalachian Range, they are, geographically, sufficiently significant to afford them a separate listing in a topographical description of Virginia. The Blue Ridge Mountains, located between the Potomac and the Roanoke Rivers, cross Virginia in a northeast-southwest direction and are from three to twenty miles wide. The Blue Ridge of Virginia originates at the junction of the Potomac and the Shenandoah Rivers and continues southwestward to the North Carolina line. From a distance the mountain ridges usually appear to be covered with a blue haze; therefore, the term "Blue Ridge" is believed to have originated from such an observation in early colonial Virginia days. This region constitutes a distinct contrast to the Piedmont area since the ridges appear abrupt yet lofty in height: in the northern half of Virginia, Stony Man Ridge (4,010 feet) and Hawksbill (4,049 feet); in the central part, Peaks of Otter (Flat Top--4,001 feet and Sharp Top--3,875 feet) and in the southwestern part, White Top Mountain (5,520 feet) and Mount Rogers (5,719 feet), the highest point in Virginia. In the southern part, the Blue Ridge becomes a rugged plateau with stony land and jagged ravines unsuited for commercial agricultural pursuits. This entire area is heavily forested with white pine, white oak, poplar, hemlock, black oak, yellow pine, chestnut, locust and chestnut oak trees. The famous Skyline Drive in the Shenandoah National Park extends one hundred miles along the crest of the Blue Ridge Mountains in this area from Front Royal to Waynesboro.