THE NATIVE genius of the American people is for seeking out fellow travelers across the vastness of a continent, and forming groups. Such groups may be founded on the most compelling or the most banal of excuses; they may be composed of people from the margins of society, or from the mainstream. But modern America in its essence is a country of subcultures, a place where a person's identity is shaped to a peculiar extent not by class, profession or place of birth but by the private enthusiasms which he or she may pursue with kindred spirits within an identifiable microcosm.

In the summer of 1977, I worked at a KOA campground in the Shenandoah Valley, digging ditches and leveling sites for the big RV rigs that came in off Interstate 81. Late in the afternoon they'd start rolling in -- the Winnebagos, the Holiday Ramblers, the big Avions and Corsairs, the jury-rigged pop-up campers molded into the sagging beds of Chevy trucks. By nightfall we'd have them all hooked up for water and sewage, and the woods would glow like a snug little village.

But over in a far section of the campground, there would usually be a cluster of identical silver trailers that looked like spacepods from Mars. They were the Airstreams, the Cadillacs of the RV industry. The Airstreamers were organized into a kind of national family called the Wally Byam Caravan Club, named for the inventor of their distinctive silver bubble.

Whether the other campers envied the Airstreamers or hated them, they had to concede that the Wally Byam Club had an interesting gig going. The Airstreamers were the proud land yachtsmen of the interstate highway system. They all had numbers affixed to their trailers, an identifying hieroglyph that only other Airstreamers could decipher. They traveled the country in caravans and attended a huge national rally on the Fourth of July. We noticed that the Airstreamers liked to camp together, so over time we got to where we automatically stuck them off by themselves in a suburban enclave.

It struck me as strange and marvelous that even in the unassuming world of RVing, there had developed a code of association. What had once been a pastime had evolved into something more elaborate -- something that might be called a society.

A few years later, I lived in the little milltown of McCall, Idaho, where I worked for a time for a weekly newspaper. By the lake just outside of town there was a tribe of hippies who lived communally out of an abandoned school bus. They were friendly, good-natured, trusting to a fault. They smelled of fragrant patchouli oil and marijuana resins. Their kids had names drawn from the flora and fauna of the American West, names like Sequoia, Buzzard, Joshua Tree. They grew their own vegetables, baked their own bread and sold hand-woven shoulder bags for spare cash.

Yet unlike most counterculturalists who lived on thousands of isolated communes across America, they were connected to something larger; they were part of a loose-knit tribe that called itself the Rainbow Family of Living Light. The McCall Rainbows had their hearts fixed on the following July, when another gathering would begin in another forest somewhere in America.

I will always remember the look of childlike expectation that shone in their faces when they talked about those gatherings. For the Rainbows, the calendar year was not a seamless procession of days, but a season built around one magical date that could be counted on like the coming of the full moon. Their bus might break down, the law might haul them off to jail, they might go broke and have to move on. But come July there was going to be a Gathering. And as always, the old faces would greet them with a wide smile and a kiss, and for a week they would move together in the larger rhythms of the Family. It's been said that Americans are the true existentialists -- that we have no general national character other than each American's individual desire to create his own universe. Our culture is steeped in cliches of rugged individualism -- Thoreau on Walden Pond, Teddy Roosevelt riding the Dakota plains, Natty Bumppo alone in the deep forest.

Yet despite our jealously guarded myth of self-reliance, Americans, like people everywhere, need to feel an allegiance to a community. If Americans are existentialists, then we are social existentialists. We want to follow our own dreams, but we don't want to do it alone. Harley-Davidson bikers often claim to be heirs to the cowboy individualism of the Wild West, but they dress identically, ride around in gangs and attend huge rallies of fellow "Hog" owners. Boxcar hoboes, perhaps the ultimate individualists in America, have held an annual gathering in Britt, Iowa, for more than 100 years. They call it, without a trace of irony, The National Hobo Convention.

Alexis de Tocqueville, in his visit to the United States in the 1830s, was astounded by what he called our "art of association." He marveled at the extraordinary diversity of groups that seemed to spring up without any provocation or encouragement from the government -- the innumerable fraternal orders, charity organizations, temperance societies and civic clubs. As a people, he observed, we did not take well to monolithic organizations, preferring instead to create smaller fellowships of like-minded souls. "Secondary associations," he called them.

In the last half-century, a different variety of "secondary association" has emerged. An economic boom unparalleled in world history gave Americans of all classes the leisure time and disposable income to live a new kind of life. It has liberated us from our farms and factories and allowed us to define ourselves by our play. Increasingly, we are cell-dividing into a thousand insular isms and odd little clans, many of them built around the once marginal concern of "lifestyle." Just as our professional worlds are forever partitioning into new subdisciplines, so too is our taste for avocation and whimsy. We've become a land of refined fanaticism. We choose our flavor of lifestyle and we go in deep.

Anything you could dream of doing, you can probably find a society of Americans who are already doing it, and doing it so intensely that they've organized their lives around it. They return each year to the tribal stomping grounds. They subscribe to the national magazine. They buy the requisite tools and toys. They decorate their cars with esoteric bumper stickers and vanity plates. They build up a circle of friends in the group. They meet their spouse in the group. They rear their children in the group. They spend their vacations doing whatever the group does. By degrees of emotional and financial investment, they get themselves submerged.

The 1991 edition of the "Encyclopedia of Associations," the bible of booking agents and talk-show hosts, lists more than 22,000 U.S. organizations. There are 1,174 hobby and avocational organizations indexed in the "Encyclopedia," 839 athletic and sports organizations and 580 fan clubs -- including 25 Elvis societies and five devoted to the TV series "Star Trek."

The Conchologists of America, headquartered in the unlikely marine capital of Louisville, Ky., is for "individuals interested in mollusks." The Aladdin Knights of the Mystic Light, in Simpsons, Ill., is for "collectors, dealers, users and admirers of Aladdin lamps." If you're a majorette, you might look into the National Baton Twirling Association of Janesville, Wis.

It is this superabundance of options in America that makes people throw up their hands and choose a single thing with countervailing conviction. Perhaps the faithlessness of the modern age forces them to claim their own absolutes.

But more likely, loneliness is at the root of the subculture explosion. In many cases, these groups have become extended families. They are filling the void left by the erosion of the neighborhood, the church, the political party, the fraternal order, the trade union. They are fighting alienation in the suburbs and offering a hand of stability to the children of transience and divorce.

It should not be too surprising that subcultures are flourishing most intensely in places that lack rootedness and a sense of place -- notably, in the condo kingdoms of coastal Florida and the tract-housing sprawls of Southern California. People want to belong somewhere. People want to be masters of at least one small corner of the universe. The growth of American subcultures has been fueled in part by technological advances in communications. A devotee can stay in instantaneous contact with his fellows across four time zones, while bathing himself in images constantly beamed down from the subcultural headquarters. And the headquarters can be just about anywhere. Running a new subculture is a cinch. Gone are the PR obstacles that have foiled visionaries down through the ages. Martin Luther had to nail his 95 theses to the church door. Today he'd just put them out via satellite.

Lee Baxandall, founder of the Naturist Society, one of America's principal nudist organizations, runs his subculture out of a small Main Street office in the town of Oshkosh, Wis. With a few choice tools, he's managed to turn his shop into the Mission Control of Nudism. He's installed a computer bulletin board and an 800 number. He desk-publishes a four-color nudist magazine and receives faxes from fellow nudists around the country. When he steps inside his office, he is no longer living in Oshkosh; he is living in Nudistland.

Physical geography is gradually being supplanted by the social geography of "lifestyle." A Mary Kay saleslady in Missoula, Mont., probably has less in common with the lady down the street than she has with a fellow Mary Kay saleslady in Milford, Mass. In the hierarchy of distinguishing traits, it's no longer so much a question of where you live; it's what you're "into."

Madison Avenue has responded to the segmenting of popular culture in increasingly subtle ways, giving rise to a new genre of industry buzzwords ("narrowcasting," "targeted advertizing," "micromarketing," "niche marketing"). A few years ago a book by Michael J. Weiss entitled "The Clustering of America" used an elaborate formula derived from postal ZIP codes to suggest that marketing professionals could break down the country into precisely 49 neighborhood types, each with its own descriptive tag: "Blue Blood Estates," "Furs and Station Wagons," "Shotguns and Pickups."

The fishing world is a good example of the phenomenon. It used to be that the average angler would subscribe to a general-purpose outdoors magazine such as Field & Stream. He ventured into the wilderness with a vague sense of himself as an American Sportsman. It was all pretty simple: He grabbed a few cane poles and a Mason jar full of night crawlers, and he went fishing.

Today, he is more likely to concentrate on a single variety of fish, like the large-mouth bass, and buy the full arsenal that technology has devised for its capture. He owns a $20,000 metalflake bass boat with a sonar depthfinder, a pH meter and a foot-operated trolling motor. He gets Bassmaster magazine in the mail and tunes in to the various bass shows on his satellite dish. He joins the local chapter of the BASS society, and he knows more about the behavior of the bass than he knows about his next-door neighbor.

He is no longer an American Sportsman; he is something more fully realized. He is a Bassmaster.

Ray Scott, the millionaire entrepreneur from Alabama who more or less invented the whole bass-fishing subculture, grasped the phenomenon as far back as 1967. Scott called it the "verticalization of America." Our culture was balkanizing, metastasizing, splintering into deep subspecialties. Scott thought that if a businessman could turn on his radar and identify one of these untapped "vertical" markets, he could make a fortune, first by awakening people to the existence of a lifestyle, and then by amplifying people's desire to practice it with acumen and a sense of high fashion.

"One of the great things about this crazy country of ours is that you can specialize in anything," Scott told me in 1989. "Hell, you can specialize in salt and pepper shakers if you want. Or better yet, just salt shakers. In my case, I specialized in a single species of fish and built a whole world on it." People so often say that America is becoming all the same, that the golden arches have swallowed the soul of the country. And certainly the surface layers have been stripped and bulldozed into sameness. But scratch the surface, and you find a vast archipelago that is unimaginably wild and lush. If you want to see the diversity of America, you just have to go island-hopping.

There is, of course, a darker side to the American passion for joining groups. The United States has always been fertile ground for the formation of hate groups, bizarre sects and netherworld gangs. The Ku Klux Klan is only one of the more sordid examples of our "art of association." And we have always produced our share of spiritual mountebanks who pull in lost souls and rob them blind. But the occasional racist group or cult of High Weirdness is the small price we pay for the freedom to associate however we please.

Who knows how long the fragmentation of the republic will continue? Maybe sometime in the next 50 years, the oil will run dry and we'll move back to our farms and villages and stay put for awhile. Or maybe some new invention, a time machine or human transfer device like the Beam Me Up Scottie, will alter the social landscape in unforseen ways.

Yet the laws of human nature that produced the subculture archipelago will never change. This nation of 250 million social existentialists will always need the fellowship of smaller tribes. We will continue to crave the ritual of the group gathering.

And we will keep returning, season by season, to the stomping grounds.

Hampton Sides is writing a book on American subcultures, which will be published by William Morrow.