Under a buzzing fluorescent light in the third-floor conference room of the Hispanic Housing Development Corporation’s offices in Humboldt Park, 30 Puerto Rican community leaders hover over their Styrofoam cups of coffee, discussing the same topic that has been discussed for 20 years at this monthly gathering: the menace of gentrification.

Members of an organization called the Puerto Rican Agenda, they effectively serve as the neighborhood’s war council. It’s a seasoned bunch—the average age is around 50—consisting of shop owners, real estate developers, professors, and plenty of rabble-rousers. Their conversation is mostly in English, punctuated, when things get heated, with bursts of Spanish.

At one end of the L-shaped table, the unofficial leader, Jose Lopez, sits quietly. But when a question arises about whether Humboldt Park’s east side could really lose its Latino identity in the next 10 years, he gears up quickly. “I’ve been doing this a long time, and I can tell when we’re really under threat,” he says, his hands flat against the table, pushing himself forward. “And we’re really under threat. Gentrification is here.”

He overarticulates every word, as if to underline each one. Gen-tri-fi-ca-tion. His voice is raspy, and he peppers his language with charged verbiage such as “revolution,” “colonialism,” and “the American dream.” Lopez, 65, has spent his life fighting for the rights of Puerto Ricans, both on his home island and in his adopted Chicago neighborhood, where he has lived since moving to the mainland with his family in 1959. He has built two community centers and a mental health facility, has helped run several campaigns for local politicians, and was critical to the creation of a new neighborhood high school—all while teaching the history of Latin America at Northeastern Illinois University. (Representative Luis Gutierrez, who hails from Humboldt Park, was one of his early students, in the mid-1970s.)

Across the table, Hipolito “Paul” Roldan, an old friend of Lopez’s and CEO of the nonprofit Hispanic Housing Development Corporation, perks up. “The barbarians are at the gate!” he says. Lopez nods in agreement. “We’ve accomplished a lot over the past 25 years,” Lopez says. “But we need to be smart about how to move forward. If we don’t get together now, we’re going to be displaced.”

It’s a funny notion: Birkenstock-wearing, craft-beer-swigging millennials as barbarians. But to understand what has Lopez so alarmed, you first have to understand what Humboldt Park represents to him and many other Puerto Rican Chicagoans.

On any given Saturday, Division Street, Humboldt Park’s main artery (dubbed Paseo Boricua), is full of Puerto Ricans packing the patios at restaurants such as Papa’s Cache Sabroso and La Bruquena, drinking rum cocktails and picking at roasted chicken, tostones, and black beans. The sound of traditional bomba and plena music echoes across the wide street, where groups of teenage boys ride their bikes while sucking down cups of watermelon juice from one of the neighborhood food carts. Old men, cigarettes hanging from their mouths, gather in the park itself—gorgeous, sprawling—to play dominoes. There is a rootedness to this place, a palpable sense of community.

Adorned with two 59-foot steel sculptures of Puerto Rican flags (which Lopez campaigned to erect) and dozens of murals celebrating Puerto Rican culture, Humboldt Park has become not only one of Chicago’s largest Puerto Rican enclaves but also the cultural, and political, heart of that community. Over the past five decades, Chicago’s Puerto Rican population has nearly tripled. Of the 103,000 Puerto Ricans who now call Chicago home, 16,000 live in what the Puerto Rican Agenda defines as Humboldt Park: the three square miles bordered by Western, Pulaski, Chicago, and Armitage (that definition differs some from the city’s and real estate agents’). Fifty-seven percent of the neighborhood’s residents are Latino; 24 percent, Puerto Rican.

As Latino neighborhoods gentrify one by one across the Northwest Side—first Bucktown, then Wicker Park, and more recently Logan Square—Humboldt Park remains one of the last holdouts. “What’s happening is, populations are being displaced and dispersed across Chicago,” says Lopez. “And then it’s mostly white, wealthy newcomers who come in and do not care about preserving cultural identity. They want to get rid of it and erase it.”

For Lopez, the fight against gentrification is a matter of preserving not just community but also clout. From 1990 to 2010 (the year of the most recent census), the number of Latinos in Chicago ballooned by 233,000, to nearly 779,000, or 29 percent of the city’s population. But as a group, Latinos don’t carry as much political power as their numbers would indicate. That’s partly because gentrification has diluted their leverage in neighborhoods where they once formed the majority. (The 2012 redrawing of Chicago’s 50 wards left only 13 that were mostly Latino; if the map accurately reflected the city’s demographics, that number would be 15.)

Which is why Humboldt Park’s Puerto Rican Agenda, representing such a concentrated voting bloc, holds considerable sway with the City Council’s 15-member Latino Caucus—three of whom represent wards that cut through the neighborhood. Recently, for example, Lopez and his allies met with two of the aldermen to push for raising the affordable-housing requirement on new multiunit residential developments in their wards from 10 to at least 20 percent of units.

It’s no wonder that Lopez is so bent on defending what he calls “nuestro pequeño pedazo de tierra” (our little pocket of land).

His plan for fending off gentrification largely involves shoring up the community. In other words, self-gentrification. Humboldt Park, like many ethnic pockets, is plagued by unemployment (17.3 percent vs. 12.9 percent for the city), crime (15.6 violent crimes per 1,000 residents last year vs. 7.5 for the city), and other problems of poverty. Lopez rattles off a list of goals that includes strengthening schools, securing loans for Puerto Rican business owners, offering job training for parents, and expanding affordable housing for low-income Latinos. “A community should be an ecosystem,” he says. “You must have people of all different incomes. It should be a shared space.”

Over the years, Lopez has managed to put up considerable roadblocks to outside development. In 2004, for example, he worked with Alderman Billy Ocasio to establish the 26th Ward Affordable Housing Committee. That initiative prevented developers from building anything in the district bigger than a single-family home without the committee’s approval. But Ocasio is no longer in office, and with him went the committee.

While Lopez is not without his critics—some see his line-in-the-sand stance against gentrification as outdated and unrealistic (more on this later)—many neighborhood residents look at this squat (5-foot-6), often abrasive man as a paladin in earth-toned shirts and orthopedic shoes. “Jose is, to great extent, the cultural soul of Humboldt Park,” says Hispanic Housing’s Roldan. “He is irreplaceable, as far as I’m concerned. I really wonder about what would happen if Jose keeled over. Who will be left to champion all of these crucial causes to sustain the Puerto Rican community in Chicago?”

Humboldt Park wasn’t always a Latino stronghold. As late as the 1950s, the neighborhood was a stew of Scandinavian, Polish, German, Russian, and Italian immigrants. But as migrant workers began to come to Chicago for industrial jobs, and as white families flocked to the suburbs, Humboldt Park, like many working-class neighborhoods, started to change rapidly. By 1960, more than 32,000 Puerto Ricans were living in Chicago, nearly all of them recent arrivals. The lion’s share settled in Humboldt Park and neighborhoods to its north and east.

Among those new arrivals were Lopez and his family. His father, Alberto, came to Chicago in 1951, hoping to find work (he took a job at a company that made steel pipes for pipelines), and brought over his wife and six children eight years later. The adjustment was difficult on the nine-year-old Jose, who was one of a handful of new Puerto Rican kids at his school. “I remember on our first day, the teacher gave us a book to read, but we couldn’t read English,” says Lopez. “So they put us in the coatroom. That was quite a shock—the isolation and the marginalization.”

By the mid-1960s, the city was awash with social unrest, much of it falling along racial lines. In 1966, a 21-year-old man was shot by police in Wicker Park the same day as the city’s first Puerto Rican People’s Parade. Rioting erupted on Division Street in Humboldt Park and lasted three days. Lopez, then a 16-year-old bookish militant who religiously read Muhammad Speaks, the Nation of Islam’s newspaper, witnessed it all. “People were getting on tops of roofs and throwing down bricks and garbage on the police,” he recalls. “That really impacted me—the level of violence and the frustration that people were expressing. Humboldt Park was literally a battleground. It really brought to light the whole sense of exclusion. We were living in an area that was both a slum and a ghetto.”

Growing up in Puerto Rico, Lopez was instilled with a fierce sense of nationalist pride. His mother, Andrea Rivera—the daughter of Jose Elias, one of the founding members of the Puerto Rican Independence Party, the electoral arm of the Puerto Rican independence movement—used to recite nationalist poems to him at bedtime. (Lopez remains a staunch advocate for the movement, traveling to Puerto Rico and throughout the United States to promote independence.)

That sense of pride stayed with him in his new home. After graduating in 1968 from Humboldt Park’s now-defunct Tuley High School, Lopez enrolled at Loyola University. He had opportunities to go elsewhere, including Cornell University, but decided to stay close to home. “I knew if I left the city, I’d leave this community, and I wanted to be embedded here.”

Lopez earned a history degree at Loyola and in 1971 went to work as a teacher at Tuley. At 22, he began leading seminars on Latin American history—the pedagogical equivalent of the nationalist poems he had heard as a baby. Around that same time, he met his first wife, Myrna Salgado, a Humboldt Park resident and activist. They had two daughters, Maria Andrea and Lolita Paina. (Lopez has been married and divorced twice.)

In the early ’70s, Lopez and his older brother Oscar Lopez Rivera became heavily active in local issues affecting the Latino community, including housing rights and equal pay. In 1973, they worked together to create the Puerto Rican Cultural Center in Humboldt Park. (Lopez still serves as the executive director of the nonprofit, which seeks to promote ethnic identity and runs daycare centers, creative writing workshops, and other programs for residents.) They also led the effort to open Roberto Clemente Community Academy, a high school in the neighborhood that would be more accommodating to students whose first language was not English and more sensitive to Puerto Rican culture.

But by 1975, the brothers had grown apart. Rivera had become involved with the Armed Forces of National Liberation (or FALN, by its Spanish initials), a radical group that sought to transform Puerto Rico into a Communist state. It had been a while since they’d seen each other when Lopez ran into Rivera in a Humboldt Park alley in the spring of 1976. Recalls Lopez: “He says, ‘I’m going to be leaving. I just want to make sure the work we have started continues.’ I thought he was going to Puerto Rico! But when the five o’clock news came, it said ‘FALN bomb factory.’ I began to put things together.”

After eluding authorities for five years, Rivera was arrested in 1981 on numerous federal charges related to the FALN, which was linked to more than 100 bombings across the United States. He was convicted of, among other crimes, seditious conspiracy, a charge reserved for those plotting to overthrow the government, and sentenced to 55 years in prison. (He was later given an additional 15 years for conspiring to escape.) “In many ways, we chose very different paths,” says Lopez of his brother. “When he came back from the Vietnam War [in 1967], he was much more radicalized. For me, it was easier to negotiate and see the world in a very different way.”

Over the next decade, Lopez led a national campaign for the release of his brother and other FALN members. In 1999, President Clinton offered Rivera a reduced sentence (some other members were given clemency), but he did not accept, effectively turning himself into a martyr and symbol for the Puerto Rican independence movement. To this day, “Free Oscar Lopez” posters dot many storefronts in Humboldt Park.

“It’s been very, very difficult. It was devastating for my mother,” says Jose Lopez, who occasionally makes the four-hour pilgrimage to the prison in Terre Haute, Indiana, where his brother, now 71, is held. “Nevertheless, when people believe in something deeply and hold on to it, they know there are consequences. I think he lives with a level of serenity.”

From a corner table at Café Colao, a Humboldt Park coffee shop that Lopez’s family started and later sold, Lopez looks out on Division Street. He can often be found here, holding forth on radical politics. He wipes the sweat off his forehead with a napkin, catching his breath. It’s only 11 a.m., and he’s already been running all over the neighborhood, to meetings at Clemente and the cultural center.

Over the course of an hourlong conversation, he swings back and forth between quiet reflections on his life in Puerto Rico and aggressive rants about the plight of his people. At one point, he goes off on a five-minute tangent about racism. “The westward expansion of the United States was driven by the idea that pioneers reshaped the land in their image,” he says, the deep grooves under his eyes shadowed in the late-morning light. “That idea still drives a lot of newcomers in this area.” As Lopez talks, a bomba version of “I Will Survive” plays in the background, a fitting soundtrack to his lecture.

Like his brother, Lopez revels in the hard line. But the war he’s waging may be an unwinnable one. All you have to do is look around the Northwest Side to understand that gentrification is coming, whether Lopez likes it or not. These days, you can hardly spill a cocktail in bordering Logan Square without hitting a farm-to-table restaurant, a small-batch brewery, or a refurbished condo. But what that neighborhood has gained in development and hipster cachet, it’s lost in affordable rents and Latinos. Between 2000 and 2010, the number of Latinos living in Logan Square dropped by 15,000, shrinking their share of its population from 71 to 58 percent.

That kind of shift is typical, says Richard Taub, an urban sociologist at the University of Chicago who has spent his career studying Chicago neighborhoods. “It’s wishful thinking to want an ethnic pocket,” Taub says. “Cities are dynamic and they don’t stand still. There are very few places in Chicago that have been stable over a 20-year period. Change is hard to fight.”

In fact, change has already begun in Humboldt Park. At the start of this year, the online real estate brokerage Redfin projected that Humboldt Park would be one of the 10 hottest neighborhoods in the country in 2014. Sure enough, over the last year, the median house price in Humboldt Park has jumped 42 percent, to $260,000.

Another harbinger of change: Brendan Sodikoff, a restaurateur with eight eateries across the city (Au Cheval and Bavette’s Bar & Boeuf, among them) and a knack for picking Chicago’s next hip neighborhood, announced in June that he’s opening two restaurants just a few blocks from the park in Humboldt Park. “It’s the next frontier—that’s how I feel about it,” he has said of the neighborhood.

Sodikoff’s projects are only the latest additions to a string of small stores that have moved in, including Humboldt House, a midcentury modern furniture shop; Meadowlark, a vintage clothing store; and the Arborist, a used-furniture retailer—all three hallmarks of hipsterdom. “These businesses are totally problematic,” Lopez says. “Why create a series of small businesses that cater totally to a white population?”

Lopez has his own ideas for the kinds of businesses Humboldt Park needs: a bicycle factory (he also wants to increase the number of bike lanes and create a bike-share program), weekly markets where residents sell their produce, Puerto Rican bars that serve Caribbean spirits, and a theater that produces the work of Latino playwrights. “Developers should be about creating a city where people can coexist,” he says.

While Lopez’s lofty vision galvanizes many in the community, it alienates others. “Jose is one of the smartest people I know, but there’s a difference between understanding complicated theories and actually making things happen,” says Julio Urrutia, who worked under Lopez as the deputy director of the Puerto Rican Cultural Center before leaving in 2012 to become a political consultant. “You can’t stop gentrification. You can’t out-organize it; you can’t outthink it. Jose is really driven by fear of losing control of the neighborhood.”

That reluctance to cede power may be one reason Lopez and other community figures have fallen short in fostering the next generation of leaders, says Urrutia. “There’s no one who’s going to step in for Jose. My feedback to him is, Who have you been developing? Who are the people who are going to carry on this work when you’re gone?”

Urrutia, 29, could have been one of those people, but frequent clashes with Lopez drove him away, he says. Removed from the radical politics of the 1960s and ’70s, Urrutia and others of his generation take a more moderate stance when it comes to gentrification. Walking around Humboldt Park, I ask several Puerto Rican teenagers if they know who Lopez is (they don’t) and whether they are excited about the new businesses opening up (they are). “The question is whether they will continue identifying as Puerto Rican or even as Latino,” says Ralph Cintron, an English and Latin American studies professor at the University of Illinois at Chicago and a member of the Puerto Rican Agenda. “It’s not clear to me how many of them care about the idea of Puerto Rican nationalism. And within a couple of generations, they will care even less.”

No amount of criticism or skepticism is going to stop Jose Lopez from fighting what he considers to be the good fight. The latest armor in his battle against gentrification involves the neighborhood schools—specifically, Community as a Campus, an innovative and comprehensive proposal he has spent five years devising. A better-educated, better-trained population, he reasons, is less likely to be displaced.

The plan calls for aligning the curriculum in all of Humboldt Park’s schools, from preschool through high school, to emphasize dual-language education, Latin American history, and group discussion. In addition, some of the 11 elementary schools would have a specialty (one might focus on the arts, for example, and another on math and science), and parents could send their children to the school of their choice, not just the one they are zoned for. “If you’re a wealthy white person, your child can go to the best school,” says Lopez. “Poor families should also have that choice.” The plan also involves setting up satellite classrooms around the neighborhood (hence the program’s name)—at the police station or library, say—where public employees would help instruct students.

Ultimately, the success of Community as a Campus hinges on improving the school that all of the elementaries feed into: Clemente, the only public neighborhood high school on Humboldt Park’s east side and historically one of the worst performers in the city. (It has been on academic probation 18 years running.). The 3,100-capacity school sits nearly three-quarters empty, with just 900 students last year; others have flocked to charter and selective enrollment schools elsewhere.

Lopez’s plan has the support of Mayor Emanuel, Chicago Public Schools CEO Barbara Byrd-Bennett, and the Chicago Board of Education. But the district still needs to nail down a structure for how the schools could accomplish their own agenda while still complying with CPS requirements. Another hurdle is financial. The program’s budget calls for up to $4 million in private funds, in addition to those from CPS. No money has been raised yet, though Lopez is working with the nonprofit Local Initiatives Support Corporation to write grant proposals.

One key step has already been taken. Clemente was one of five public high schools in Chicago selected by the mayor’s office in 2012 to adopt “wall-to-wall” International Baccalaureate programs, a push Lopez helped lead. The IB curriculum focuses on hands-on learning rather than teaching to standardized tests, and students who graduate from IB schools are 45 percent more likely to attend a four-year college, according to the University of Chicago Consortium on Chicago School Research. In only one year of IB, Clemente’s graduation rate shot up from 56 percent to 68 percent, just below the citywide 69 percent.

Lopez believes that Community as a Campus could turn Humboldt Park into an incubator for Chicago’s next wave of global citizens: bilingual, highly skilled workers. But even if the program proves a raving success, there’s another issue. Over the past decade, a large percentage of educated middle-class Latinos have left Humboldt Park for better jobs elsewhere. Call it bright flight. “As a general rule, Hispanics really are following the route of other immigrants who came into this country,” says the University of Chicago’s Taub. “Which is, they congregate in a particular area where the prices are right, and then they start to make it and become upwardly mobile, eventually moving to other places.”

All of which raises a nagging question: Can Lopez improve his neighborhood without changing the people who live there?

His continued insistence that he can, without ever directly addressing the inherent dilemma, lends a Don Quixote air to his sermons at Café Colao. A neighborhood woman stops by his table to chat; a button on her lapel reads “Free Oscar Lopez.”

Later, I ask Lopez if he thinks his brother has given up too much for the struggle. He looks down at his hands. “It’s a lot to sacrifice,” he says, circling his palms around the table as though he were cleaning it. “But I think when you live a life that’s selfless, one that’s based on justice, in the end that’s a life worth living.”