Question: How long is the extension of the blue ridge mountain range that Nichol's Gap Road was built over?

full_context: Document 1: Blue Ridge Parkway: The Blue Ridge Parkway is a National Parkway and All-American Road in the United States, noted for its scenic beauty. The parkway, which is America's longest linear park, runs for 469 mi through 29 Virginia and North Carolina counties, linking Shenandoah National Park to Great Smoky Mountains National Park. It runs mostly along the spine of the Blue Ridge, a major mountain chain that is part of the Appalachian Mountains. Its southern terminus is at U.S. 441 on the boundary between Great Smoky Mountains National Park and the Cherokee Indian Reservation in North Carolina, from which it travels north to Shenandoah National Park in Virginia. The roadway continues through Shenandoah as Skyline Drive, a similar scenic road which is managed by a different National Park Service unit.
Document 2: Susquehanna and Tioga Turnpike: The Susquehanna and Tioga Turnpike; also called the Berwick and Tioga Turnpike, and Susquehanna & Tioga Turnpike connecting via the high ground of tributary valleys Berwick and upstream, Tioga—chartered & incorporated in 1806, the toll road, like many middle ages toll roads in Europe was opened initially as a animal power (foot traffic) turnpike in northeastern Pennsylvania (eventually) connecting early Central & Northern Eastern Pennsylvania along the Main Branch Susquehanna River to Lower New York State. Established in the early American canal age, and undercapitalized , it took several years to gradually extend improved trails in stages 100 mi to Elmira, New York from its southern terminus at Berwick, Pennsylvania opposite Nescopeck across the Susquehanna River—in this manner it initially also sufficed as a bridle trail as well. Where demand existed from sources of natural resources or farmers seeking to ship farm goods to markets, it was systematically widened and improved into a wagon road.
Document 3: Elk Ridge (Maryland): Elk Ridge is a mountain ridge of the Blue Ridge Mountains in Maryland. The ridge is located to the west of South Mountain and runs roughly parallel to it from Rohrersville, in the north, to the Potomac River across from Harpers Ferry, West Virginia, in the south. Across the Potomac the ridge continues as Blue Ridge Mountain in Virginia and West Virginia. The southern end of the ridge, which is part of Harpers Ferry National Historical Park, is known as Maryland Heights.
Document 4: Federal Road (Creek lands): The Federal Road through the territory of the Creek people was a project that started in 1805 when the Creek gave permission for the development of a "horse path" through their nation for more efficient mail delivery between Washington City (modern-day Washington, D.C.) and New Orleans, Louisiana. This section started at Fort Wilkinson near Milledgeville, Georgia, and ended at Fort Stoddert near Mobile, Alabama. By the time of the War of 1812, the Federal Road began in Augusta, Georgia, ran through Fort Hawkins (in Macon, Georgia), on to Fort Mitchell, Alabama (near modern Phenix City, Alabama), and finally terminated at Pensacola in Spanish West Florida.
Document 5: Wilderness Road: The Wilderness Road was one of two principal routes used by colonial and early national era settlers to reach Kentucky from the East. Although this road goes through the Cumberland Gap into southern Kentucky and northern Tennessee, the other (more northern route) is sometimes called the "Cumberland Road" because it started in Fort Cumberland in Maryland. Despite Kentucky Senator Henry Clay's advocacy of this route, early in the 19th century, the northern route was selected for the National Road, connecting near Washington, Pennsylvania into the Ohio Valley of northern Kentucky and Ohio.
Document 6: Roan Mountain (Roan Highlands): Roan Mountain is the highpoint of the Roan-Unaka Range of the Southern Appalachian Mountains, located in the Southeastern United States. The mountain is clad in a dense stand of Southern Appalachian spruce-fir forest, and includes the world's largest natural rhododendron garden, and the longest stretch of grassy bald in the Appalachian range. The Cherokee National Forest and Pisgah National Forest converge atop the mountain, with Roan Mountain State Park located near its northern base. The Appalachian Trail crosses most of the Roan's crest. The Roan High Knob Shelter is the highest backcountry shelter on the entire 2174 mi trail.
Document 7: Cumberland Valley: The Cumberland Valley is a northern constituent valley of the Great Appalachian Valley, within the Atlantic Seaboard watershed in Pennsylvania and Maryland. The Appalachian Trail crosses through the valley.
Document 8: Pennsylvania Route 97 (Adams County): Pennsylvania Route 97 (PA 97) is a state highway in the U.S. state of Pennsylvania. Known for most of its length as Baltimore Pike, the highway runs 9.363 mi from the Maryland state line near Littlestown, where the highway continues as Maryland Route 97 (MD 97), northwest to U.S. Route 15 (US 15) near Gettysburg. PA 97 connects Gettysburg and Littlestown in southeastern Adams County. The highway also links those communities with Westminster and Baltimore. From PA 97's northern end, Baltimore Pike continues toward Gettysburg through the Gettysburg Battlefield Historic District, where it provides access to the Gettysburg Museum and Visitor Center.
Document 9: Carolina Road: The Carolina Road or the "Old Carolina Road" are names for various sections of the Great Wagon Road and other routes in colonial America. "The 'Old Carolina Road', extending from Lancaster, Pennsylvania to the Yadkin Valley, was one of the most heavily traveled roads in eighteenth century America." Parts of the 180 mile long Journey Through Hallowed Ground National Heritage Area scenic byway follows the Old Carolina Road through Pennsylvania, Maryland and Virginia.
Document 10: Nichol's Gap Road: The Nichol's Gap Road was a central Pennsylvania highway established in the 18th century near Maryland extending westward from the Black's Gap Road "just west of Little Conewago Creek" at the "Crofs Keys" stand of James Black. The road was past both the Rock Creek Church and 1761 Samuel Gettys tavern where Gettysburg would be surveyed in 1786. The highway was built over the South Mountain (Maryland and Pennsylvania) via Nichol's Gap ( ) and down the Devils Racecourse into the Cumberland Valley, allowing access to the 1762 Hagerstown, Maryland. Called the "Hagerstown Road" during the Battle of Gettysburg, parts of the road are now designated (east-to-west): U. S. Route 30 in Pennsylvania, Pennsylvania Route 116 (Fairfield Road to Fairfield, Pennsylvania), Iron Springs Road, Gum Springs Road, and Old Route 16 (the summit section through Nichol's Gap--"Fairfield Gap" during the American Civil War—no longer has a roadway.)
Document 11: Blue Ridge Mountains: The Blue Ridge Mountains are a physiographic province of the larger Appalachian Mountains range. This province consists of northern and southern physiographic regions, which divide near the Roanoke River gap. The mountain range is located in the eastern United States, starting at its southernmost portion in Georgia, then ending northward in Pennsylvania. To the west of the Blue Ridge, between it and the bulk of the Appalachians, lies the Great Appalachian Valley, bordered on the west by the Ridge and Valley province of the Appalachian range.
Document 12: Pennsylvania Route 132: Pennsylvania Route 132 (PA 132) is a state highway in southeast Pennsylvania. It runs northwest to southeast through Bucks County in suburban Philadelphia from PA 611 in Warrington Township to Interstate 95 (I-95) in Bensalem Township. It is a commercial route lined with shopping centers throughout much of its 15 mi length. It is named Street Road and is five lanes wide for much of its length. It was also designated as the Armed Forces and Veterans Memorial Highway in 2005. From west to east, it crosses PA 263 and PA 332 in Warminster Township, PA 232 in Upper Southampton Township, PA 532 in Lower Southampton Township, and U.S. Route 1 (US 1), the Pennsylvania Turnpike (I-276), PA 513, and US 13 in Bensalem Township. Street Road was included in William Penn's survey plans and completed by 1737. The road was paved by 1911 and received the PA 132 designation by 1927. The road was widened into a multi-lane highway and extended to I-95 by 1970. An E-ZPass-only interchange with the Pennsylvania Turnpike opened in 2010.
Document 13: South Mountain (Maryland and Pennsylvania): South Mountain is the northern extension of the Blue Ridge Mountain range in Maryland and Pennsylvania. From the Potomac River near Knoxville, Maryland, in the south, to Dillsburg, Pennsylvania, in the north, the 70 mi range separates the Hagerstown and Cumberland valleys from the Piedmont regions of the two states. The Appalachian National Scenic Trail follows the crest of the mountain through Maryland and a portion of Pennsylvania.
Document 14: Malden Inn: The 1820s Malden Inn (also sometimes as "The Kreppsville Inn") and John Krepps Tavern is a historic building in the unincorporated bedroom community of Malden, Pennsylvania at the junction of South Malden Road and Old U.S. Route 40 (US40), the historic Cumberland Pike. The Inn's Malden location (present-day borough of Centerville, PA) along the western part of the Amerindian trail known as Nemacolin's Path transformed into a wagon road linking the river ford between Brownsville–West Brownsville with the former frontier towns of Washington, Pennsylvania and Wheeling, West Virginia, where the Emigrant Trail then allowed an easy crossing the Ohio River. The Inn had a good commercial site astride the old National Pike (U.S. Route 40 before the 1960s highway construction project) about three miles west of the long climb up from West Brownsville and Denbo Heights, PA being located at the former junction of Malden Road connecting northwards to Coal Center and California situated about half-the-way to Centerville from the Brownsville ford and the ferry terminus below Blainsburg just North-northeast of West Brownsville.
Document 15: Piedmont Mountains: The Piedmont Mountains are outlying mountains, sometimes called “low mountains”, that typically occur in the western Piedmont near the Blue Ridge. Most of the features within the Piedmont physiographic region of North America lie either on the eastern border where the plateau plunges onto the Coastal Plain at the Fall Line, in the broad valleys of the river systems, or on the western border where Piedmont Mountains likely occur. Occasionally, due to diverse rock formations, folds and outcroppings, these mountains can rise at various locations across the Piedmont like the Uwharrie Mountain Range in North Carolina or the Pine Mountain Range in Georgia. Most of these mountains, or hills, are what is left of ancient eroded mountains. Some, like Stone Mountain in Georgia, are solitary rock domes called Monadnocks which become further exposed with erosion. The Piedmont is part of the greater Appalachian Mountain Range and is also referred to as the Appalachian Plateau. The French definition of piedmont in itself translates as foothill; however, a Piedmont Mountain may be that of greater significance or prominent elevation.
ground_truth: 70 mi