Amtrak runs two main services from Penn Station to Washington Union Station: the Acela, which takes around 2 hours 45 minutes, and the Northeast Regional, which takes approximately 3 hours 30 minutes. The Acela is significantly more expensive; the Regional is more than adequate for a two-night trip where arrival time is not critical. Trains run frequently. Book in advance and book your seat; Amtrak assigned seating is worthwhile for a journey this length.
Washington Union Station is centrally located in northeast Washington. The Metro's Red Line runs from Union Station to most of the city's main hotel corridors, including Dupont Circle, downtown and the area nearest the Mall. Uber and Lyft operate throughout the city and are often faster than the Metro for specific journeys.
The structure of this trip matters. Two nights in Washington, on legs that have just run 42.195 km, works best if the pace is deliberately slow. The Smithsonian complex alone is large enough to fill two days without any external pressure to keep moving, and the museums are free.
The Smithsonian Museums
The Smithsonian Institution operates nineteen museums in Washington, most of them clustered along the National Mall between the Capitol and the Lincoln Memorial. All are free. The relevant question is not which ones to visit but which ones can be visited at the pace legs allow on days one and two after a marathon.
National Museum of Natural History (10th Street and Constitution Avenue NW) is the least physically demanding: the main galleries occupy a single sprawling floor, with the hall of gems (containing the Hope Diamond), the ocean hall with its suspended blue whale, and an extensive human origins exhibition. There are benches throughout. Allow two to three hours for a non-rushed visit.
National Air and Space Museum (6th Street and Independence Avenue SW) is the most visited museum in the United States. The main hall has the Wright Brothers' Flyer, Charles Lindbergh's Spirit of St. Louis, and a section of lunar rock visitors can touch. It is large and crowded even in November; go early and plan to leave before the afternoon school-group peak. Two hours is sufficient.
National Portrait Gallery / American Art Museum (8th and F Streets NW) is a single building housing two separate collections. The Portrait Gallery's American Presidents hall and the American Art Museum's 20th-century collection are both substantial; the shared central atrium has café seating. This is the best choice for an afternoon when the Mall feels too far.
The National Mall
The National Mall is a flat, grassed corridor two miles long from the Capitol steps to the Lincoln Memorial. Both ends and the Washington Monument in the middle are significant; walking the full length on post-marathon legs is a question of how much the legs object.
If only one section: the Washington Monument end offers the monument itself, the Vietnam Veterans Memorial (black granite wall sunk into a gentle slope, below eye level, deliberately quiet) and the Lincoln Memorial at the far end. The Vietnam Memorial requires descending into and ascending out of a shallow valley; the gradient is small but noticeable when legs are sore.
The Capitol building offers tours (book well in advance online) or can be viewed from the steps without a reservation.
Georgetown
Georgetown is the most walkable residential neighbourhood in Washington: a street grid of 18th and 19th century rowhouses above the Potomac, with independent bookshops, restaurants and cafés on M Street and Wisconsin Avenue. The area is approximately 20 minutes by taxi from Union Station or from most central hotels.
Martin's Tavern (1264 Wisconsin Avenue NW) has been open since 1933 and is the longest continuously operating family-owned restaurant in the city. John F. Kennedy proposed to Jacqueline in Booth 3. The menu is classic American bar food done competently. It opens at 11am and does not take reservations.
The C&O Canal towpath along the Potomac is flat, unpaved and quiet in November; a twenty-minute walk along it in either direction is a reasonable post-marathon river walk without the additional gradient that gets into Georgetown via the main streets from the Metro.
Getting Back to New York
Amtrak from Washington Union Station to Penn Station. Book the return ticket in advance for the best fares. The Northeast Regional on the return is perfectly comfortable for a three-hour journey if the Acela premium is not worthwhile. Union Station's main hall is one of the better waiting rooms on the East Coast: high-ceilinged, with adequate food options and seating.