Question: Union Square is located at the foot of which historic neighborhood in Washington, D.C.?

Context paragraphs:
Union Square (Somerville): Union Square is a neighborhood in the southeastern part of Somerville, Massachusetts.  It is centered on Union Square proper, which is located at the intersection of Washington Street, Webster Avenue, and Somerville Avenue.

Union Square, Manhattan: Union Square is an important and historic intersection and surrounding neighborhood in Manhattan, New York City, located where Broadway and the former Bowery Road – now Fourth Avenue – came together in the early 19th century; its name denotes that "here was the union of the two principal thoroughfares of the island" rather than celebrating either the Federal union of the United States or labor unions .  The current Union Square Park is bounded by 14th Street on the south, Union Square West on the west side, 17th Street on the north, and on the east Union Square East, which links together Broadway and Park Avenue South to Fourth Avenue and the continuation of Broadway.  The park is under the aegis of the New York City Department of Parks and Recreation.

Union Square (Washington, D.C.): Union Square is an 11-acre public plaza at the foot of Capitol Hill in Washington, D.C., USA.  It encompasses the "Ulysses S. Grant Memorial" (1924) and the 6-acre Capitol Reflecting Pool (1971) and is just west of the United States Capitol building.  Views differ as to whether the Square is just east of the National Mall or is itself the eastern end.

Union Square, Boston: Union Square is a square in the Allston neighborhood of Boston, Massachusetts at the intersection of Cambridge Street and Brighton Avenue/North Beacon Street.  Union Square is serviced by the MBTA 57, 64, 66, 501, and 503 buses.  There is also a station for the Hubway bicycle sharing system in Union Square.

Capitol Hill: Capitol Hill, in addition to being a metonym for the United States Congress, is the largest historic residential neighborhood in Washington, D.C., stretching easterly in front of the United States Capitol along wide avenues.  It is one of the oldest residential neighborhoods in Washington, D.C., and with roughly 35,000 people in just under 2 mi2 , it is also one of the most densely populated.

University Place (Manhattan): University Place is a short north–south thoroughfare in Manhattan, New York City, which runs from Washington Square Park in the south as a continuation of Washington Square East, taking the position of Madison Avenue uptown, and terminates at East 14th Street just southwest of Union Square.  Although the roadway continues north of 14th Street as Union Square West, the two streets run in opposite directions (University Place uptown, and Union Square West downtown), both feeding into 14th Street.  Until the late 1990s, University Place was a two-way street.  The street contains numerous shops and restaurants, many of which cater to students at NYU and The New School.

Union Square Cafe: Union Square Cafe is an American restaurant featuring New American cuisine, located at 101 E 19th St (between Park Avenue South and Irving Place), in the Union Square neighborhood of the Manhattan borough of New York City, New York.  It is owned by the Union Square Hospitality Group.

East 17th Street/Irving Place Historic District: The East 17th Street/Irving Place Historic District is a small historic district located primarily on East 17th Street between Union Square East and Irving Place in the Union Square neighborhood of Manhattan, New York City.  It was designated by the New York City Landmarks Preservation Commission on June 30, 1988, and encompasses nine mid-19th century rowhouses and apartment buildings on the south side of East 17th Street, from number 104 to number 122, plus one additional building at 47 Irving Place just south of 17th Street.

Abraham Lincoln (Brown): Abraham Lincoln is an outdoor bronze sculpture of Abraham Lincoln by Henry Kirke Brown, located at Union Square in Manhattan, New York.  Cast in 1870 and dedicated on September 16 of that year, the statue was originally installed at the southwest corner of Union Square, where the sculpture of Mahatma Gandhi stands today.  In 1875, a stone and bronze rail fence was constructed around the statue of Lincoln; the fence included an inscription of text from his second inaugural address, “…with malice toward none; charity toward all.”  During the 1930 redesign of Union Square Park, the statue was moved to its current location, but the fence remained.  The statue is in axial alignment with the Independence Flagstaff and "George Washington".  It was conserved in 1992.

Washington Irving Campus: The Washington Irving Campus is a public school building located at 40 Irving Place between East 16th and 17th Streets in the Gramercy Park neighborhood of Manhattan, New York City, near Union Square.  Formerly the Washington Irving High School (until 2008), it now houses the Gramercy Arts High School, the High School for Language and Diplomacy (established 2009), the International High School at Union Square (established 2010), the Union Square Academy for Health Sciences (established 2012), and the Academy for Software Engineering (established 2012)—under the New York City Department of Education.  One floor of the building houses the Success Academy Charter School.

Supporting paragraphs: Union Square (Washington, D.C.) Capitol Hill
Answer: Capitol Hill