Question: Which river runs through the Shenandoah National Park and is a tributary of the Potomac River?
Context: The Cold Spring River is a 3.9 mi mountain stream in Rockingham County in the U.S. state of Virginia.  It is a tributary of the German River, the principal source of the North Fork Shenandoah River.  Via the Shenandoah River, the Cold Spring River is part of the Potomac River watershed. Shenandoah National Park (often ) is a national park that encompasses part of the Blue Ridge Mountains in the U.S. state of Virginia.  The park is long and narrow, with the broad Shenandoah River and Valley on the west side, and the rolling hills of the Virginia Piedmont on the east.  Although the scenic Skyline Drive is likely the most prominent feature of the park, almost 40% of the land area 79579 acre has been designated as wilderness and is protected as part of the National Wilderness Preservation System.  The highest peak is Hawksbill Mountain at 4051 ft . Green Spring Run is an 8.9 mi tributary stream of the North Branch Potomac River in Hampshire County in the U.S. state of West Virginia.  Green Spring Run rises in Greenwood Hollow north of Springfield and meanders northeast through Green Spring Valley.  The South Branch Valley Railroad and Green Spring Road (West Virginia Secondary Route 1) run parallel to the stream.  It runs through the community of Green Spring, from which the stream takes its name.  From Green Spring, Green Spring Run flows east where it reaches its confluence with the North Branch Potomac shortly before the North Branch joins with the South Branch Potomac River to form the Potomac River. The Baltimore and Ohio Railroad is the oldest railroad in the United States and the first common carrier railroad.  It came into being mostly because the city of Baltimore wanted to compete with the newly constructed Erie Canal (which served New York City) and another canal being proposed by Pennsylvania, which would have connected Philadelphia and Pittsburgh.  At first this railroad was located entirely in the state of Maryland with an original line from the port of Baltimore west to Sandy Hook.  At this point to continue westward, it had to cross into Virginia (now West Virginia) over the Potomac River, adjacent to the confluence of the Potomac and Shenandoah rivers.  From there it passed through Virginia from Harpers Ferry to a point just west of the junction of Patterson Creek and the North Branch Potomac River where it crossed back into Maryland to reach Cumberland.  From there it was extended to the Ohio River at Wheeling and a few years later also to Parkersburg, West Virginia. Plantations that operated within the present-day boundaries of West Virginia were located in the counties of the Ridge-and-Valley Appalachians and in the Kanawha and Ohio River valley regions.  Beginning in the mid-to-late 18th century, members of the Washington family and other prominent Virginia families began to build elegant Georgian mansions on their plantations in the Ridge-and-Valley Appalachians region of present-day West Virginia.  Plantations initially developed in the counties lying within the Northern Neck Proprietary of Thomas Fairfax, 6th Lord Fairfax of Cameron within the Shenandoah Valley and South Branch Potomac River valleys.  Slavery as practiced through plantations in the American South was carried over from the plantations of the Piedmont and Tidewater regions of Virginia, where plantations had become the foundation of society and industry.  Following the French and Indian War, settlement and agricultural development continued unabated in the Shenandoah and South Branch Potomac valleys.  Early instances of western Virginia plantations with grand homes include the John Ariss-designed Harewood (1774) for George Washington's brother Samuel Washington and Happy Retreat (1780) built by Washington's younger brother Charles Washington, both of which are located near Charles Town in present-day Jefferson County.  In Hampshire County, Nicholas Casey constructed a Georgian mansion (1774) at his Wappocomo plantation, one of the first plantation houses of its kind in the South Branch Potomac River valley. Bear Rocks are a widely recognized symbol of West Virginia wilderness and among the most frequently photographed places in the state.  They are a well-known landmark on the eastern edge of the plateau that includes the Dolly Sods Wilderness.  They sit in a high-elevation heathland punctuated with wind-carved sandstone outcrops and is home to more than a dozen rare plant and animal species.  Situated on the crest of the Allegheny Front, Bear Rocks afford vistas over the South Branch Potomac River.  Visibility can extend eastward to the Shenandoah National Park in Virginia. Potomac Creek is a 16.7 mi tidal tributary of the Potomac River in King George and Stafford counties, Virginia.  Potomac Creek's source lies between the communities of Glendie and Paynes Corner in Stafford County.  It empties into the Potomac River at Marlboro Point.  Potomac Creek forms as a dam to form Abel Lake. East Potomac Park is a park located on a man-made island in the Potomac River in Washington, D.C., in the United States.  The park lies southeast of the Jefferson Memorial and the 14th Street Bridge, and the Washington Channel lies between the park and the Potomac River.  Amenities in East Potomac Park include the East Potomac Park Golf Course, a miniature golf course, a public swimming pool (the East Potomac Park Aquatic Center), tennis courts, and several athletic fields (some configured for baseball and softball, others for soccer, rugby, or American football).  The park is a popular spot for fishermen, and cyclists, walkers, inline skaters, and runners heavily use the park's roads and paths.  A portion of Ohio Drive SW runs along the perimeter of the park. The Shenandoah River is a tributary of the Potomac River, 55.6 mi long with two forks approximately 100 mi long each, in the U.S. states of Virginia and West Virginia.  The principal tributary of the Potomac, the river and its tributaries drain the central and lower Shenandoah Valley and the Page Valley in the Appalachians on the west side of the Blue Ridge Mountains, in northwestern Virginia and the Eastern Panhandle of West Virginia. 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.
Answer: Shenandoah River