Arlington House is the historic family residence of Robert E. Lee, commander of the Confederate Army, and a national memorial in his honor serving as a museum, located in Arlington, Virginia. It is situated in the middle of Arlington National Cemetery, overlooking the Potomac River and the National Mall. Built by Lee's father in law G.W.P. Custis in 1803-1818, Arlington House is a Greek Revival style mansion designed by the English architect George Hadfield. Its garden and adjoined structures are also preserved. During the U.S. Civil War, the mansion was used as U.S. army headquarters and its grounds were selected as the site of Arlington National Cemetery, in part to ensure that Lee would never again be able to reside there. Arlington House is part of the Arlington National Cemetery Historical Region on the National Register of Historic Places. Although the United States Department of the Army maintains Arlington National Cemetery, the National Park Service administers Arlington House. There, the U.S. flag flies at half-staff during funerals. Construction and early history The mansion was built on the orders of George Washington Parke Custis, the foster son of George Washington and grandson of Martha Dandridge Custis Washington. Custis became a prominent resident of an area that was then known as Alexandria County, at the time a part of the District of Columbia. Arlington House was built at a high point on a 1,100-acre (445 ha) estate that Custis's father, John Parke Custis, had purchased in 1778 and named "Mount Washington" ("Jacky" Custis died in 1781 at Yorktown after the British surrender). The younger Custis decided to build his home on the property in 1802 following the death of Martha Washington and three years after the death of George Washington. After acquiring the property, Custis renamed it "Arlington" after the Custis family's homestead on the Eastern Shore of Virginia. Almost immediately, Custis began constructing Arlington House on his land. Hiring George Hadfield as architect, he constructed a mansion exhibiting the first example of Greek Revival architecture in America. Custis intended the mansion to serve as a living memorial to George Washington and a place for his collection of George Washington artifacts. Its design included elements similar to those of George Washington's house, Mount Vernon. Construction began in 1803, eleven years after L'Enfant's Plan for the future "Federal City" (later called "Washington City", then Washington D.C.) had designated an area directly across the