The Museum's grand entry hall, Milestones of Flight showcases a truly awesome collection of historic aircraft and spacecraft that represent epic achievements in aviation and space flight. The place of honor at the center of the gallery is reserved for the 1903 Wright Flyer, which is temporarily on exhibit in its own gallery upstairs.
Some of the other aviation achievements celebrated here: Charles Lindbergh's solo trip across the Atlantic in his Spirit of St. Louis; the first American jet aircraft, the Bell XP-59A Airacomet; the Bell X-1 in which "Chuck" Yeager first broke the mythical "sound barrier"; and the fastest aircraft ever flown, the North American X-15.
Some space triumphs represented here: the Mercury capsule Friendship 7 flown by John Glenn; the Apollo 11 command module Columbia from the first lunar landing mission; Mariner, Pioneer, and Viking planetary explorers; and the first privately developed, piloted vehicle to reach space, SpaceShipOne. You can even touch a Moon rock here.
From the Air and Space Museum's web page: http://www.nasm.si.edu/exhibitions/gal100/index.cfm