College Park Aviation Museum
College Park, Maryland
This small, Smithsonian-affiliated museum is at the world's oldest continually operating airport, which opened in 1909 when Wilbur Wright arrived to provide flight instruction to America's first military aviators. Airplanes on display date back to 1910. Among the many firsts at this site: the first woman in an airplane (as a passenger), and the first bombs dropped and machine guns fired from a plane.
One of the museum's airplanes -- and they're all old airplanes here -- was the first open-cockpit biplane to reach the North Pole. Another, from the 1920s, is the world's first helicopter, although the museum notes that it was "unable to perfect a safe and smooth landing." The 1910 Wright Model B was the first airplane with wheels.