Question: What Union Occupied estate near Fort Craig overlooks the Potomac River ?
Context: The Potomac Highlands of West Virginia (or Potomac Highlands) (   ) centers on five counties (Grant, Hampshire, Hardy, Mineral, and Pendleton) in the upper Potomac River watershed in the western portion of the state's Eastern Panhandle, bordering Maryland and Virginia.  Because of geographical proximity, similar topography and landscapes, and shared culture and history, the Potomac Highlands region also includes Pocahontas, Randolph, and Tucker counties, even though they are in the Monongahela River or New River watersheds and not that of the Potomac River. Fort Craig was a small crescent-shaped, Civil War-era fort built by the Union Army in Arlington County (at that time Alexandria County) in Virginia.  It was part of the defensive ring around Washington, D.C. and was occupied throughout the American Civil War.  Fort Craig stood less than a mile away from Arlington House, the Union-occupied estate of Confederate General Robert E. Lee. Arlington House, The Robert E. Lee Memorial, formerly named the Custis-Lee Mansion, is a Greek revival style mansion located in Arlington, Virginia, United States that was once the home of Confederate General Robert E. Lee.  It overlooks the Potomac River and the National Mall in Washington, D.C. During the American Civil War, the grounds of the mansion were selected as the site of Arlington National Cemetery, in part to ensure that Lee would never again be able to return to his home.  However, the United States has since designated the mansion as a National Memorial to Lee. 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. The South Branch Valley Railroad (reporting mark SBVR) consists of a 52.4 mile (84.33 km) length of railroad in the U.S. state of West Virginia extending north along the South Branch Potomac River from Petersburg to the CSXT mainline at Green Spring adjacent to the Potomac River.  At Green Spring, the CSXT mainline connects the SBVR to Cumberland, Maryland to the west and Martinsburg, West Virginia to the east.  SBVR has been owned and operated by the West Virginia State Rail Authority (SRA) since it was sold by the Baltimore & Ohio Railroad on October 11, 1978.  Upon purchasing the B&O's South Branch line, West Virginia became the first state in the United States to both own and operate a commercial freight railroad.  In 1985, major flooding of the South Branch Valley destroyed most of the rail line, including all three bridges that crossed the South Branch Potomac River.  Despite talk of shutting down the railroad after the flood, reconstruction began two years later. The Doubleday Hill Monument is an American Civil War monument located in Williamsport, Maryland, in what is now River View Cemetery.  Erected in 1897, the monument commemorates the crossing of the Potomac River and occupation of the hill by Major General Abner Doubleday.  The monument, also known Doubleday Hill, overlooks the Potomac River into West Virginia. 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. Pope Branch is a tributary stream of the Anacostia River in Washington, DC.  The headwaters of the stream originate near Fort Davis Drive, and the branch flows roughly northwest for about 1 mi to the Anacostia, which drains to the Potomac River and the Chesapeake Bay.  The watershed area of Pope Branch is about 0.4 sqmi . 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 Battle of Aquia Creek was an exchange of cannon fire between Union Navy gunboats and Confederate shore batteries on the Potomac River at its confluence with Aquia Creek in Stafford County, Virginia.  The battle took place from May 29, 1861 to June 1, 1861 during the early days of the American Civil War.  The Confederates set up several shore batteries to block Union military and commercial vessels from moving in the Chesapeake Bay and along the lower Potomac River as well as for defensive purposes.  The battery at Aquia also was intended to protect the railroad terminal at that location.  The Union forces sought to destroy or remove these batteries as part of the effort to blockade Confederate States coastal and Chesapeake Bay ports.  The battle was tactically inconclusive.  Each side inflicted little damage and no serious casualties on the other.  The Union vessels were unable to dislodge the Confederates from their positions or to inflict serious casualties on their garrisons or serious damage to their batteries.  The Confederates manning the batteries were unable to inflict serious casualties on the Union sailors or cause serious damage to the Union vessels.  Soon after the battle, on Sunday, July 7, 1861, the Confederates first used naval mines, unsuccessfully, off the Aquia Landing batteries.  The Confederates ultimately abandoned the batteries on March 9, 1862 as they moved forces to meet the threat created by the Union Army's Peninsula Campaign.  The U. S. National Park Service includes this engagement in its list of 384 principal battles of the American Civil War.
Answer: Arlington House