AT THE SMITHSONIAN'S National Postal Museum, trucks and planes are the time-travel machines of choice. Two new transportation-themed exhibits return kids to the days of horseless wagons, the Wright brothers' plane and the first manned space flight.

"On the Road" takes youngsters through the bumpy history of motorized mail delivery. Though it shares a title with Jack Kerouac's classic novel, the small permanent exhibit reveals an American road experience very different from the Beat author's wild ride. The display and a video focus on the pitfalls, pratfalls and potholes that brought the U.S. Postal Service from the first Winton motorcar in 1899 to today's fleet of 188,600 specially designed vehicles.

You want funny? The video shows vintage footage of the motley trucks cobbled together during the Depression and World War II, when economic and wartime woes prevented development of new models. And it gets funnier. In 1957, a much-touted new model, the Mailster, proved to be a three-wheeled lemon that was easily halted by snow and toppled by large dogs. Frustrated mail carriers quickly embraced the next new thing -- a modified go-anywhere jeep, widely used for the next 20 years but now nearly phased out.

The exhibit includes a 1931 Model A Ford Parcel Post truck and a 1986 Grumman Long Life Vehicle, the white rectangular model that delivers 600 million pieces of mail daily. Both are set in replicas of the city streets of their time. On a recent visit, my daughter Christy, 61/2, enjoyed pointing out differences between then and now with the display's sidewalks, roads, streetlights and distribution boxes. Life-size models of two mail carriers show changes in uniforms, bags and even gender. The switch from male to female acknowledges the nearly 91,000 women employed as carriers today.

Next Christy and I traveled from street to sky by entering the nearby "Stamps Take Flight," a year-long exhibit that continues to March 19. The stamps offer a window into the history of both aviation and stampmaking. Largely drawn from the Postmaster General's Collection, begun in the 1860s, the exhibit features original artwork and designs for such well-known stamps as the 1918 "Inverted Jenny," with its plane image printed upside down, and the 1962 4 cent Project Mercury stamp, which was designed and printed under secrecy and released minutes after John Glenn's successful Earth orbit.

Especially intriguing is the wall of more than 200 different flight stamps issued by the Postal Service from 1913 to 2003. The broad sweep provides a kind of who's who of air and space travel. Christy and I had a good time picking out Orville and Wilbur Wright's plane (1913), pilots Amelia Earhart (1963) and Bessie Coleman (1995), the moon landing (1969) and a cartoon Snoopy atop a doghouse plane (2001). The stamps' chronological arrangement highlights changes over time in stamp technique and artistry, from carefully detailed engravings and monochrome palettes to colorful lithographs and gravures. Christy noted that 1963's Earhart stamp sold for 8 cents, 1974's Skylab for 10 cents and 1998's Charles Lindbergh for 32 cents.

With such a wide range of styles and content, family members will have fun naming a favorite stamp. Christy chose Earhart, her favorite aviator; I got a kick out of the cheery drawing of a rocket-enclosed kid, with the inscription "Mommy, are we there yet?" (2000).

We then touched down in the museum's Ford Education Center, which is supported by the Ford Motor Company Fund (sponsors as well of the "On the Road" exhibit). The center's five computers allow visitors to conduct searches, try various activities and read about historical objects.

Christy played several stamp memory games, created a virtual collection of horse and butterfly stamps and did research on Owney, the canine mascot of the late-19th-century Railway Mail Service. As happens sometimes with researchers, my daughter fell in love with her subject, whose mail-train adventures took him across the country and around the world. Christy's growing admiration prompted the sending of an Owney postcard to her grandparents and the gift-shop purchase of her own plush pup.

NATIONAL POSTAL MUSEUM -- 2 Massachusetts Ave. NE in the Old City Post Office Building (Metro: Union Station). 202-633-1000 or 202-357-2020. Open daily 10 to 5:30; closed Dec. 25. Free. The museum focuses on the history of the nation's mail service and holds the world's largest collection of stamps and philatelic material. Hand-held electronic devices that display text and play an audio recording are available free at the kiosk in the atrium.


Reservations are not required, but groups larger than 20 should call 202-633-5533 to ensure adequate accommodation.

Saturday 1 to 3 -- Kids visit "On the Road" exhibit, participate in interactive story and puzzle, and design postal vehicle. Designed for ages 5 to 10, but all ages welcome. Children must be accompanied by an adult. Free.

July 29 noon to 4 -- Activities, such as stamp design, focus on "Stamps Take Flight" exhibit. All ages. Free.

Aug. 13 1 to 4 -- A workshop devoted to Owney, the canine mascot of the Railway Mail Service. "Dog-tag" craft, scavenger hunt, and readings and signings by authors of two books about Owney, Irene Kelly's "A Small Dog's Big Life" and Dirk Wales's "A Lucky Dog." Designed for ages 5 to 10, but all ages welcome. Children must be accompanied by an adult. Free.

The National Postal Museum's "On the Road" exhibit traces the history of motorized mail delivery in America. Project Mercury stamps were printed secretly in 1962.Flight stamps have honored aviation giants such as Amelia Earhart.A Snoopy stamp in the aviation- themed "Stamps Take Flight."Some stamps in "Stamps Take Flight" have a more whimsical view of flying.These 1913 U.S. parcel post stamps were 20 cents.