THE UNITED STATES is a nation of travelers. If you weren't born here, then you traveled to get here. If you were born here, chances are one of your earliest memories is a traveling one: sitting in your parents' car and going, riding through some part of the vast American landscape. We are a people on the move. Our pop culture is scattered with road references. Hit the road, Jack. Route 66. On the road. On the road again. Country road. Highway 61 revisited. Road rules. Road trip!

The National Building Museum continues to tap smartly into the things that have made this country what it is with its latest exhibit, "See the U.S.A.: Automobile Travel and the American Landscape." It traces the link between the automobile and the near-mythic wanderlust that has permeated our national imagination from the very start. As soon as Henry Ford figured out how to mass produce his snappy black roadsters, that was all she wrote. Americans took to the road in droves, forever altering the landscape they were out to see. No longer tethered to the fixed schedules of trains and boats, Americans jumped on that ultimate expression of personal freedom: the road trip.

Walking into the exhibit space, you're greeted by a Model-T Ford, sitting there on four skinny wheels, the top down, just begging you to jump in. On the floor is painted a huge map of the United States, lined with the first highways. Hey look! There's Route 1, Route 11, Route 70. There's Laramie! Miles City! Buffalo! A country linked by the internal combustion engine.

Stand to the side and watch people as they enter. Watch them look down, tracing trips taken earlier in this incredible century. You note immediately the genius of this exhibit. It's one big memory jog. No matter how old you are, try to go with someone of an older generation (most of what's relevant here precedes the development of the interstate highway system of the '50s and '60s). If you can't make that happen, then eavesdrop on people as you stroll through. "Oh, I remember that!" is something you hear a lot while walking through. People stop at the two actual gas pumps and point: "Remember when you actually had to pump the gasoline? And it went up into that container on top first so you could see how much you were actually getting?"

Scattered throughout the exhibit, complementing the larger objects are old maps, old postcards, photographs and drawings that send you reeling back through the years. There's the tunnel through the giant redwood. There's the tepee motel. There's a Dairy Queen.

Things are set up so that you understand very clearly what the consequences of car travel were. Cars needed gas, so gas stations popped up, then inevitably evolved into something more complex: service stations. Places to put air in your tires, get a map, go to the bathroom, get some coffee. Coffee? What about a meal? The entire fast-food industry was built around the automobile. Why do you think Howard Johnson's roofs were orange? A motorist could spot 'em a mile off. Not fast enough? How about a drive-in? A drive-thru? All are lovingly represented here.

And what about sleeping, after a wearisome drive across the Plains? Hotels weren't the ticket. You didn't need a fancy lobby and room service. You needed a cheap place to sack out. You needed a "drive-thru" hotel -- a motel. Feast your eyes on the examples of motels that guest curator John Margolies has photographed over the years (don't miss his superb books in the museum gift shop, including "Home Away From Home: Motels in America.").

And what about the roadside attractions? Places like "Dinosaur-land" and "South of the Border"? Margolies writes in the nicely thought-out exhibition notes that these were "an energetic hodgepodge of discordant elements often considered to be unattractive and `tacky' when compared to traditional concepts of `good taste.' " But you can tell from this exhibit that he fell in love with them, unconditionally, at an early age. What a pain he must have been in the backseat of the family car! Always begging to stop, stop, stop and see the alligator wrestling! But we're lucky he followed his passion. This is the stuff, for better and worse, that has defined this country. The car and its consequences, "tacky" and otherwise.

There's not much discussion here of the environmental degradation brought about by exhaust fumes and highway construction, by billboards and shopping malls. There's not much examination of the people left out of all this generally joyful travel, the hobos and the Dust Bowl drifters. The question of segregation in the road experience is barely touched on (there's one little book, "The Green Book: The Negro Motorist" from 1946, which listed accommodations for African Americans). For the most part, this is a happy show, an ode to the automobile. Hey, if you want the downside, just hop on the Beltway.

SEE THE U.S.A.: Automobile Travel and the American Landscape" -- Through May 7 at the National Building Museum, 401 F Street NW (Metro: Judiciary Square). 202/272-2448.

Web site: www.nbm.org. Open Monday-Saturday 10 to 4, Sunday noon to 4. Building tours weekdays at 12:30, weekends at 12:30 and 1:30. Suggested donation of $3.

CAPTION: On a postcard, a Howard Johnson's restaurant in Waynesboro, Va., beckons motorists to come in and have a bite to eat.

CAPTION: Above, the Mystery Spot in St. Ignace, Mich., used intrigue to draw visitors.

CAPTION: A painting of dinosaur replicas, at left, by Donald Jacot captures the kitsch of the Wheel Inn outside Cabazon, Calif.