Saturday night a new bar called Fly opens on Divisadero Street in San Francisco’s once working-class Western Addition neighborhood, and it immediately becomes a magnet for prosperous white kids. Sunday evening, the St. John Coltrane African Orthodox Church a few blocks down the boulevard holds a benefit to raise money to help it find a new home after 29 years in a neighborhood storefront. And this isn’t even the part of town that’s changing most rapidly. What’s happening in the Western Addition is just the spillover from the wild mutation of the formerly industrial South of Market area and the formerly Latino and affordable Mission District. These are the neighborhoods most affected by San Francisco’s emergence as a center of global Internet culture.

For most of its history, San Francisco has been a refuge for free spirits and maverick minds. Soon this will no longer be true. Gentrification is transforming the city by driving out the poor, including those who have chosen to give their lives to unlucrative pursuits such as art, activism, social experimentation, or social service. But gentrification is just the fin above water. Below you’ll find the rest of the shark: a new American economy in which many of us will be poorer, a few will be far richer, and everything will be faster, more homogenous, and more closely controlled. Despite the volatility in this new economy from day to day, its long-term impact seems destined to change the cultural and political life of cities and perhaps the whole nation. The technology boom and the accompanying housing crisis have fast-forwarded San Francisco well into the 21st century; Seattle, New York, Boston, Austin, Denver, Portland, and other booming cities are not far behind. A decade ago, Los Angeles looked like the future of urban life: decay, segregation, open warfare. But the new future looks like the new San Francisco: a frenzy of financial speculation, covert coercions, overt erasures, a barrage of novelty-item restaurants, the despair of unemployment replaced by the numbness of incessant work hours and the anxiety of destabilized jobs, homes, and neighborhoods.

The Bay Area is home to 35 percent of the venture capital in this country, and 30 percent of the multimedia/Internet businesses. The broadest effect of this boom is a runaway real estate inflation. Small businesses and nonprofit groups often receive "economic evictions" when their new leases rise as much as 600 percent. Because San Francisco has rent control but not vacancy control, home evictions are at an all-time high. Seventy percent of those getting the boot leave the city. All over San Francisco, buildings are being torn down and replaced with bigger ones, long-vacant lots are being filled in, condos built and sold, old industrial buildings and former nonprofit offices turned into dot-com headquarters and upscale lofts. The many new business startups have in turn generated new boutiques, restaurants, and bars that displace existing businesses, particularly arts and social service organizations.

The influx of high-tech money has inflated real estate prices to the point that the people who hold the Bay Area together can’t afford to live there. "The brutality," writes Jeff Goodell about the region in Rolling Stone, "is apparent not just to newcomers who arrive here to seek their fortune but also to anyone who is so unwise as to choose a field of work for love, not money. Schoolteachers, cops, construction workers, nurses, even doctors and lawyers—as the tide of wealth rises around them, many are finding it harder to stay afloat."

Cities traditionally are both the administrative hub from which order, control, and hierarchy emanate and the place where that order is subverted. This subversion rises out of the free space of the city where people and ideas circulate, and bohemia is the freest space of all, a place where the poor, the radical, the marginal, and the creative overlap. Bohemia is not so much a population as a condition, a condition of urbanism to which the young go to invent themselves and from which cultural innovation and insurrection arise. As that free space contracts, the poor and individual artists will go elsewhere, but bohemia may well go away altogether, here and in cities across the country. (I use the word bohemian to mean all the participants in the undivided spectrum of radical politics and artistic culture, a spectrum that includes Marxists who look down on the arts and artists who don’t notice politics until it evicts them.)

There’s a cruel irony here. The white middle class fled America’s cities over the past 50 years, spawning the crises of disinvestment and poverty that plagued most cities from the ’60s through the ’90s, and still affects many. But the poor and the bohemians stuck with urban life, often creating a lively culture amid all the problems. Now the privileged are coming back from the suburbs, setting off a new kind of crisis. As the new economy arrives in San Francisco, it is laying waste to the city’s existing culture—in the sense both of cultural diversity and of creative artistic or political activity. It may turn out that wealth can ravage a city’s vitality even more than poverty.

And what has happened in San Francisco is beginning to happen across the country. Changes comparable to those William Saunders describes in Cambridge’s Harvard Square are happening across the country. As Saunders notes in The Boston Globe, "The square is now: more impersonal (e.g., the sales and service people are rarely familiar or interested in the buyer); more expensive (after inflation); more exclusionary (less welcoming and less affordable to eccentrics, the middle and working classes, and the marginally employed); more predictable, more uniform, and more like other places (a Gap is a Gap is a Gap). . . . Along with the square’s greater polish, luxury, and upscale taste come new subtle pressures to be rich and beautiful, constrained, and role-bound. The new red brick architecture—often replacing low, tippy, wood-frame buildings—is decorous and solid but boring. One longs for more bad taste, for more surprise, dirt, and looseness, more anarchic, un-self-conscious play. . . . I think of appealing college towns as at least somewhat bohemian. That word now applies to nothing in the square."

One Friday night a few weeks after Fly opened, I go there with a friend and look at the crowd. Clean-cut but aspiring to be cool, the women in very tight clothes and the men in very loose clothes drink big glasses of beer and saki cocktails. The name Fly, written in ’70s-style fat round letters on the illuminated plastic sign outside, evidently refers to the 1970s blaxploitation Superfly films, an unsettling reference for an upscale bar in a formerly African American neighborhood.

The nearby Church of St. John Coltrane exemplifies culture in every sense: It’s religious, artistic, ethnic, political, and social at the same time. It feeds the poor three times a week and serves as one of the last remaining links to the golden age of the Fillmore District before it was gutted by urban renewal. And as an eccentric, individualist cultural hybrid—making free jazz a sacrament—it represents what has always made San Francisco distinctive, while Fly is a commercial enterprise that could be anywhere people old enough to drink and affluent enough to appreciate hip decor congregate. But last year a new owner bought the building where the church is housed and doubled the rent, forcing them out. (Thanks to an outpouring of community support, they have found temporary digs in the neighborhood.)

The Sunday morning after my Friday night excursion to Fly, I bike the few blocks from my home of nearly two decades to the Coltrane church, which honors the peerless free jazz saxophonist and composer. One of the church’s walls is lined with glossy paintings in the Eastern Orthodox style of angels, saints, and the Madonna and child, all with dark skin. The other wall features the text of Coltrane’s classic composition, A Love Supreme. Off by itself is a smaller painting of Coltrane in Byzantine-icon style, with delicate flames inside the mouth of his saxophone. Front and center on the altar is a painting of Jesus with neat dreadlocks.

Bishop Franzo King appears, puts on what looks like a red yarmulke, and the service begins with the recitation of the Lord’s Prayer and other prayers in a formal style. But after the prayers, he begins to preach like his fellow African American Baptist and Methodist ministers in the neighborhood, fervently, rhythmically. Bishop King asks God to soften the hearts of those up high and to care for the needy below, and he says that heaven is the true home of this church that is becoming homeless. Turning sideways, I see a young Asian couple has come in and we’ve got all the races represented, if the guy with the soul patch is as Hispanic as he looks. "The strongest argument for San Francisco over, say, Dallas," my friend Catherine e-mails me from the Mission District that day, "is that here people still mix."

I skip out on Bible class to bicycle through Golden Gate Park, which begins a few blocks west of the church, and pedal past a group of children and dogs bounding across the lawn, elderly Chinese doing tai chi, slack-faced men in cars waiting to be solicited for adventures in the shrubbery, skaters dancing to a boom box, homeless people sunning themselves, and what looks to be a matador class, with three students and an instructor (but no bull) waving hot pink capes.

I come home to a phone message from the performance artist Guillermo Gómez-Peña. When I call him back, he tells me of several incidents in which Latinos were attacked or thrown out of bars in the Mission District. "It is horrible, horrible, horrible," he says, repeating what several others have told me, that the San Francisco police are busting the neighborhood’s Latino bars for every possible code infraction, thereby accelerating their turnover into enterprises catering to the wealthier and whiter new arrivals.

The Mission is named after Mission Dolores, the church built by Franciscan missionaries in the 18th century, and it has had a Latino presence virtually ever since, especially since the 1930s, but that population is now under siege—mostly by money. Guillermo tells me that 20 of his friends in the Mission have already left, and the community that drew him to San Francisco five years ago may not exist much longer.

A sampling of newspaper stories over the next few days reveals the nature of the situation all too clearly. In the San Francisco Independent there is a story, "Popular Richmond [District] Dance Studio Faces Eviction," with an aside that dance studios all over the city are losing their spaces. A week later, the San Francisco Chronicle runs a gossip item on "start-up zillionaire Marc Greenberg," his $20 million house, his half-million dollar bachelor party, and the million he paid Elton John to play at his wedding, followed a few pages later by passionate letters about what untaxed Internet commerce will do to independent bookstores and to the community they encourage.

San Francisco institutions such as Finoccio’s—probably the nation’s longest-running drag-queen revue—have lost their leases. Fear and eviction come up every day. My favorite example is a letter to "Ask Isadora," the San Francisco Bay Guardian’s sex-advice column, by a masochist who wanted to know whether he really had to obey his dominatrix by sexually servicing her elderly landlord. Though the issue for him was about the extent to which submissiveness must go, the issue for her was preserving the lease by any means necessary.

"Where will you go?" is the question tenants ask each other, and the answer is always another city, another state. A woman who works at a domestic violence shelter tells me that the entire premise of domestic violence counseling—that the spouse should leave the batterer—is being undermined by the lack of places for victims to go after their time in temporary shelters.

Much has been said about the New Urbanism, which started an architectural movement to design suburbs that resemble urban neighborhoods, but what is happening in San Francisco and other American cities is a new new urbanism in which cities will function like suburbs. The gentrification of cities, the spread of chain stores, the ability of administrators to control the increasingly subtle details of public space and public life all threaten to make urban places as bland as homogenous suburbs.

People in San Francisco speak constantly, obsessively of what is happening and mourn what is being lost. Several photographers devote themselves to documenting the vanishing places—the same kind of salvage photography once used to document vanishing indigenous cultures. After a couple of years of being stunned, San Francisco’s radical rabble is fighting back. Newly passed ballot initiatives limit growth and eliminate zoning and tax loopholes for dot-coms and the "live/work" condos that sprang up to house their better-paid workers. Dozens of demonstrations and protests brought the issues to the street—and to the offices of Bigstep.com, a particularly invasive dot-com that was occupied by hostile members of the newly formed Mission Anti-Displacement Coalition. Dancers turned a dance-studio eviction into a seige and held out for days. The walls of the Mission are covered with brilliant political posters and stencils. The two thousand bands evicted from Downtown Rehearsal, in what is widely seen as the end of San Francisco’s once thriving music scene, had a day of outdoor concerts and a million-band march. The creativity and outrage with which San Franciscans once addressed human rights and environmental issues around the world are now being spent on their own survival. People hold meetings, work on eviction defenses, write letters to editors. Many realize that the city’s rich cultural life arises out of a combination of many ethnic groups, social classes, community resources, along with those seeking the adventure of making culture, revolutions, and identity. These things are not portable; you can move the species but not the habitat. And it’s the habitat that is disappearing.

San Francisco used to be the great anomaly among American places. What happened here was interesting precisely because it was different from what was happening anywhere else. We were a sanctuary for the queer, the eccentric, the creative, the radical, for political and economic refugees. In some ways the city’s unique identity goes back to the Gold Rush, when the absence of traditional social structures produced independent women, orgiastic behavior, epidemics of violence, and an atmosphere of liberation, even amidst the greed of a boom. "They had their faults," poet Kenneth Rexroth once remarked of San Francisco’s early inhabitants, "but they were not influenced by Cotton Mather." By the 20th century, it was becoming a center for immigrant Italian anarchists, radical Wobblies, and union organizers. Carey McWilliams, editor of The Nation in the 1950s, called it "the stronghold of trade unionism in the United States." Conscientious objectors flocked here after World War II, and the poets who would later be celebrated as the Beats started coming in the 1940s and 1950s; African Americans seeking wartime jobs produced a postwar cultural flourishing of jazz and nightlife. It was also a haven for gays and lesbians early on, and remains one today for those who can afford it. It was the place where the ’60s counterculture flourished most fully, as well as a major center for punk culture and related subversions after 1977. And since the Sierra Club was founded here in 1892, the San Francisco Bay Area has been a major center for environmental activism and the evolution of ecological thinking. Feminism, human rights activism, pacifism, Buddhism, paganism, alternative medicine, dance, rock ’n’ roll, and jazz all permeate the local culture.

Of course, such a culturally dynamic city has also changed radically many times. In 1960, it was 78 percent white; by 1980, whites were less than 50 percent of the population (an ethnic diversity similar in many ways to what the city had during the Gold Rush). It has gone from being a blue-collar port city to a white-collar center of finance, tourism, and now dot-com culture. But the pace of this change has accelerated spectacularly in recent years. As Randy Shaw, executive director of the Tenderloin Housing Clinic, put it, we have had 15 years of change compressed into a couple of dozen months, and nobody saw it coming.

Among the many who lament this development is Chris Carlsson, a respected advocate of the city’s public life who runs a typesetting shop out of a big, friendly, cluttered room on Market Street. In 1981 Chris co-founded the legendary Processed World, a magazine that promoted subversion of the white-collar workplace. In the 1990s he co-founded Critical Mass, a monthly street rally of bike riders that, among other things, graphically demonstrated the role bicycles could play as sustainable transportation. Critical mass rides modeled on San Francisco’s are now held across the world.

"There’s something very exciting about the endless influx of new energy looking for something inexplicably magical," he says. "Everybody keeps coming here to renew that quest, or had until now. And that’s exactly what I think we’re losing at this moment, this endless arrival of the young, the radical, the political, the marginal, and the edgy. And if they do come, they can’t stay, or they have to find themselves a six-day-a-week job."

As Carlsson and others know, San Francisco is not only a refuge for the nation’s pariahs and nonconformists, but also a rich breeding ground of social, artistic, and political ideas. To watch this great cultural incubator become just another address for overpaid-but-overworked producer-consumers is to witness a great loss, both for the experimentalists and the wider world they have in turns entertained, outraged, and profoundly transformed. Nevertheless, the city’s capacity to sustain this profound creativity continues to decline. The diversity, memory, and complexity so crucial to its soul are being drained away. And if the trend continues, what remains may look like the city that was (or a brighter, tidier version of it), but what it once contained will be gone. San Francisco will be a hollow city—and a model of what awaits so many places in the years to come.