Picture Mr. and Mrs. Bright Young Achiever of Tomorrow - some future equivalent of her a lawyer, him a Washington correspondent, both of them crisp as celery, cool as white wine. With, you know, values.

It matters to them that they have the Audi (but only till they can afford the Mercedes), the subscription to Architectural Digest (which they laugh at for being so stuffy and nouveau), the gold American Express card, the plans for the one perfect child who says "Mummy," not "Mommy."

Imagine them making the big telephone call to Daddy. They've found their first dream house, and it's down payment time. Well, better than a house, Mrs. BYA explains. It's a genuine 1970s antique mobile home, complete with the orange plastic hacienda roof, the injection-molded Mediterranean chandeliers.

"Please, Daddy," she says. "It's got the original flamingos out front, the black-cat clock in the kitchen with the tail that swings and the eyes that roll as it ticks! The Catalina citrus shag wall-to-wall! And I almost died when I saw the old sign posted in the window: ASK ME ABOUT MASON SHOES."

But look how nowaday's spiffies grovel and claw to get into those old Georgetown houses that were built for immigrant labor on the C&O canal, those tiny brick shacks. No wonder the spiffies play so much tennis - they have to stay thin enough to get past each other on the stairs. Anyone who's lived in a mobile home would kill before willingly moving into one of those places.

America is divided into two kinds of people - those who hate mobile homes and those who live in them.

"Lord, I hate those bastards so much," Jimmy Buffett sings of the predominant architecture of Florida, where even conventional housing looks like trailers.

They are "shiny boxes" that "imprison the senses" and are a "jarring intrusion on the landscape," said the Frank Lloyd Wright Foundation in 1971, shortly before its own designs for mobile homes - the most prominent feature being that they didn't look like mobile homes - made no dent whatsoever in the American housing market.

"Its relationship to the historic notion of a home is only approximate," sneered the Saturday Review back in 1972.

Zoning regulations throughout the Washington are forbid placing them anywhere but in mobile home parks. Liberals would rather have the entire South Bronx move in next door than a trailer. But like a lot of things in this country, mobile homes have flourished like mushrooms in the nightsoil of enlightened opinion.

Mobile homes, not to be confused with recreational vehicles or campers, accounted for "21 percent of all single-family private housing starts in 1976," according to the Manufactured Housing Institute. (The industry is currently doing The Great American Name Dance. After changing trailers to mobile homes, it now fancies them as "manufactured housing.") The institute estimates that 3.6 million of them house 10 million people, and production is supposed to increase 10 percent in 1978, with 550 plants rolling them out across the country.

"Before I started photographing them, I always thought it was an upward mobility thing, that people only lived in them until they could afford to get out," says Rhoda Baer, the Washington free-lance photographer who took the pictures on these pages. Baer spent two years of her spare time and vacations photographing trailers, trailer parks and trailer-park people. It's a project that won her fame among people who hadn't even seen the pictures. "Some of the people I talked to were second-generation trailer dwellers. They totally accept themselves and their environments. What if I knocked on your door and asked you if I could photograph your house? You'd tell me to beat it.

"They never did. They're so proud."

I am touring along Richmond Highway, which is U.S.I. on one of those lethal summer days when the cars seem to float in the smog. Richmond Highway is the Tin Can Alley of Northern Virginia, with trailer parks and dealers scattered up and down the road: Harmony, AA, Audubon, Suburban and so on.

One dealer has run me off his lot for some article The Post ran about mobile homes a few years ago. Management at another mobile home park wouldn't talk to me either. Some people who make a living in this business aren't too friendly to the press, but that's understandable when you check out what's been said.

It's an ugly history that begins before World War II. A 1936 New Yorker magazine bore a cover showing a salesman selling an old streamlined trailer to two gypsies. A book called ABCs of Trailering, by Ernest Dugas tries hard to class up the act by asserting that "numberless professional men" choose trailers over houses.

"There was a real uproar around 1935 and 1936 about trailer folk, calling them gypsies and itinerants who brought malaria, that kind of thing," says art historian Jane Bishop, who astonished her fellow Ph.D. candidates in the Yale fine arts program by electing to write her dissertation on mobile homes.

I turn into the Woodley Hills-Nightingale mobile home park, looking for echt trailer-dom, the grits and gravy of the mobile home world. Woodley-Nightingale is "one of your older parks," I've been told by a mobile home salesman who urged me to go somewhere else if I wanted to see what mobile home living was really like nowadays.

The cicadas wind up and up. The pin oaks sag in the heat. I stroll into a visual banquet of about 500 vintage mobile homes, 20 or 30 years' worth of models, starting from the Korean-war era stuff, with the round windows, the nautical "land yacht" motifs that have been with us since we christened those wagons "prairie schooners."

These old ones are known as eight-wides, for their feet in width. They were superseded by 10-wides, 12-wides, and now 14-wides. Bolt two 14-wides together and you get a double-wide.

As I stroll through the Vagabonds, the Fleetwoods, the Mobile Cruisers, the Champions, I realize that I'm seeing solutions to unique architectural problems. No one, after all, ever built houses in this shape before. Curiously enough, it isn't that huge side of the mobile home that's so difficult to handle, it's the narrow end, known as the front. I see bay windows, picture windows, little slitty windows like Frank Lloyd Wright clerestories turned on end. I see diamond-shaped panes made by laying tape across the glass to give a Tudor look, or Old English, as they say in the mobile home sales literature. Anything to give "the bright open feeling not usually associated with a mobile home," as it says in the ad for the Windsor mobile home with the "pan-o-view" front.

They hang aluminum awnings and bolt on shutters, put up plastic shutters or a little slice of mansard roof. Or hoods - they'll shroud the whole little end in aluminum that leans out at the top. But the most original gesture - it could well rank, someday, with the invention of the flying buttress in Gothic cathedrals - is what I'll call the plunging buttress. The plunging buttress is a sort of decorative cantilever that runs from the roofline back to the wall of the mobile home, sometimes in matched pairs.

Nothing else is quite so original. The colors for instance - the creams and maroons and aquas with chrome strips or aluminum panels - are inspired by automobiles. The front doors, which are actually on the side, present a major architectural problem, but there are few innovative solutions beyond old-fashioned stoops and porches.

"Rustic," Pat Miller tells me, when I ask what's the latest thing in styles.

"You know, beams and fireplaces. I saw one for $20,000 that had a brass bed. That's what's happening now." Pat Miller is a divorced, 31-year-old hairdresser who pays $83.50 a month for lot rent here, including garbage pickup, sewerage and water.

She wouldn't live in anything else, she says.

"You can move them. And I feel safe. I know all my neighbors. I lived in a four-bed-room house in Woodlawn. You can have it."

"You plan to move?"

"No, I like it here. My dad lives in a mobile home park down the road, Audubon, but he doesn't like it - no trees, and the people aren't so friendly."

In fact, there are trees down there but the vibes are very different. The Audubon trailers are newer, the streets are straighter ("When the streets are straight, the mind is clear," Le Corbusier said in 1936). In fact, Audubon has that sunstruck respectability of postwar America, everything right and tight, the homes lined up like soldiers.

Woodley-Nightingale is cozier, funkier. Call it Industrial Rustic, with a hint of the old home-on-wheels spirit - they still rent spaces to recreational vehicles. Little kids and little dogs sprint around the streets - the trailers are too close to play between them comfortably. Old folks, tending tiny lawns with infinite patience, watch. People here tend to be either young or old, in keeping with national statistics that show 38.2 percent of mobile home dwellers are under 35 years of age, and 27.8 percent are over 65. Their homes range from new models in the $10,000 to $20,000 category, down to one old, small unit with a sale sign in the window: "$175 without wheels, $250 with."

"This one here, they built it in 19 and 55," says Earl M. Gibson.

His shoes are unlaced, his teeth are uncertain. He bears days of white whiskers. He is watching Tom and Jerry cartoons in his Mobile Cruiser, an eight-wide. He lights a new cigarette off the old one.

"That's why I say it's an antique. I got it for $400. That man across the street paid $1,000 for his. I borrowed money from him - $8. Anybody you can borrow money from, you can believe. I'd like to go down around Fredericksburg and buy a lot. But then I'd have to dig a well. Then I'm in trouble. You know how much that costs? Septic tank, all that stuff? I got my own yard here. How you like my apple tree? I got my garden. But I only got four tomatoes, little green ones, like marbles."

Money, owning something of your own, being part of a community, convenience. Talk to people who live in trailers, and those are the reasons you hear.

Up at Melwood Mobile Home Park, in Upper Marlboro, newlyweds Beatrice and Julio Melgarejo, one of three young couples in the park, have a dish on the wall with a picture of a trailer and the motto: "God Bless Our Mobile Home."

"When I first saw one, I thought, 'Oooh, how ugly," says Beatrice. "And I worried about lightning hitting them. But when we moved in everybody was so nice and all. When you're out, they keep an eye on your place. And you get to know something about them. You can ride by and picture everything that's inside. Like a peaked top means a living room that has a real high ceiling. We paid $7,000 for this one, and I guess someday we'd like to buy a bigger one and put it on our own land."

Dale: You pull into one of them trailer parks, you see, an' they got ever'thing. Gas, water, washin' machines, swings, septic tanks, some even got swimmin' pools.

Lu Ann: Swimmin' pools?

Dale: You bet, and grass and trees and flowers and collie dogs runni' around.

Lu Ann: Gee, it sounds like heaven.

(Ten years later)

Lu Ann: Boy, you ain't missed nothin' - cramped, miserable little old tin boxie outfits . . .

From "Lu Ann Hampton Laverty Oberlander," part of The Texas Trilogy, by Preston Jones.

An era is ending. We may not have the mobile home to kick around anymore, at least the kind we've known. Manufacturers have finally surrendered to the great weight of that tyranny known as "taste." Mobile homes get wider, longer and look more and more like stick-built houses.

"We at Burlington have taken the mobile appearance out of home living," says a flyer. "Your Burlington interior is your choice of Country Pine, Early American or Traditional decors . . ."

Zimmer homes, once the proud manufacturer of the Zipper, Zephyr and Zeppelin models, has abandoned that breezy image for big capital letters announcing: "RUSTIC AMERICAN."

"Some people still call them 'mobile homes,'" says the Fleetwood Enterprises ad. "We don't." The ad shows beamed ceilings, sunken bathtubs, Grandma and Grandpa greeting Granddaughter, a fireplace with a rough-hewn mantel.

All this is because in the American canon of taste there's no such thing as an ugly 200-year-old house. And no such thing as a 200-year-old trailer. What's more, in the 1970s, the whole dream of modernism is dead, the notion that we should break the shackles of tradition and build Le Corbusier's "machines for living."

The problem is that "most of our images of what a house looks like are culturally determined," says Steven Izenour, an architect with Philadelphia's Venturi and Rauch, and one of the designers of the Renwick Gallery show called "Signs of Life," which described the aesthetics at work in mundanities from road signs to suburban living rooms.

Talking about mobile homes is more difficult, Izenour says "That stuff changes every three months. It's very quixotic. They change like cars change. Basically, though, since you're taking architectural styles from houses, and forcing them into a limited space, what you get is strange quirky distortions."

One mobile home for sale in Virginia, for instance, features a sunken living room which is sunken all of two inches.

"The effect becomes totally two-dimensional, a paste-on look," Izenour says. But he adds that this thin and conspicuous veneering is, in itself, a tradition in American architecture. What appears to be stone facing on Mt. Vernon is, in fact, ground-up oyster shells cemented to wood.

"In the end, some of it is kind of tacky, but some is beautiful," Izenour says.

The mobile home has outgrown itself. Before 1954, mobile homes and recreational vehicles were the same. Then the 10-wide, far more clumsy than the eight-wide to tow behind a car, went into production, leading to trailerdom's own Great Schism between the homes and the RVs. Nowadays, mobile homes are rarely moved from their first sites, though owners keep the wheels on the bottoms in order to have their houses taxed as personal property, rather than as real estate.

So says Jane Bishop, Yale Ph.D. candidate in Fine Arts, and collector of somewhat more information on mobile homes than anyone is apt to ask her for.

Her Adams-Morgan living room is darkened in preparation for the slide show. Bishop cranks up her introduction.

"The first mobile homes were Roman carts called 'carrucas.' Later on, there were shepherds' huts on four wheels. During the Napoleonic wars there were collapsible living quarters, though Napoleon never lived in one. Then we had the Conestoga wagon - the prairie schooner. The first literary reference to trailers is in The Old Curiosity Shop, by Charles Dickens, published in 1846, describing Mrs. Jarley's van. There's a trailer in The Wind in the Willows.

"The first important motor trailer in American was the Chenango tent trailer in 1910. But the first big spurt of interest came after World War I. At first they were strictly recreational, but by the '30s, people were living in them. The Farm Security Administration film archive at the Library of Congress has a collection of trailer pictures, including the camps that were set up around defense plants at the beginning of World War II. After the war, the aluminum industry boomed, and wood siding vanished."

In her travels around the country, Jane Bishop has seen a four-trailer arrangement with a swimming pool in the living room; a south-western mobile home covered with spray-on Styrofoam adobe; and enough Florida rooms and carports and plastic tile roofs and tiny screw-on shutters and Royal Blue wall-to-walls to last at least several lifetimes.

Whatever time had claimed (or windstorms - trailers used to be a bit teetery before laws requiring tie-down straps), she read about.

In the '30s, for instance, the iconography of trailers - meaning the decorations and veneer that make statements about the taste and intentions of the owners - was that of mobility. Even a two-story design, by Corwin Wilson in 1936, referred to the "main cabin" and "galley." (The two-story designs have yet to catch on.)

Bishop flashes a 1949 ad. on the wall for "M System Trailer Coaches" which shows the first movement toward house-type respectability, with its "stoopless door," and "cross-ventilated kitchen". The 1949 Travelite features a raised ceiling, but also a type of squared streamlining we didn't see in automobiles until the 1955 Fords.By 1950, the M System is talking about The Suburbanite, rather than "trailer coaches," and the ad shows all the iconography of permanence - a concrete patio, shrubs and trees. A Ventura of the same era tried to have the best of both worlds: "A real home - that travels too."

"By the 1960s," says Bishop, "the stability image became more important than the mobile image, although a sort of houseboat nautical look hung on. In the 1970s, the streamlining - slanted roofs that give an impression of speed, and two-tone, car-style decoration - died out completely." Sic transit carruca.

Well, sort of. As long as an average mobile home sells for about $15,000, according to the Manufactured Housing Institute, and the average American stick-built house sells for about $48,000, there will be a market for trailers/mobile homes/manufactured housing.

But attitudes will be attitudes. The industry can boast all it wants of high standards the Department of Housing and Urban Development insists on, but the problem is that the ignorant will continue to fall back on the lazy man's intelligence, which is to say taste. As photographer Walker Evans, whose Depression pictures are now in exemplary taste, once said: "People taste because they don't know."

One of the chronic afflictions of the upper middle class, especially in this organic era, has been a taste based on authenticity - is it a real trivet, a genuine old-time oil lantern, true Saigon linen, authentic Georgian, original Federalist?In fact, the mobile home, with all its wild and derivative eclecticism, is just as "authentic" as, say, the Greek revival house of the first half of the 19th century. Or, as Andy Warhol once said: "It's not fake anything - it's real plastic."