In their view, the study reflected Salt Lake City's recent past, when the population was far more homogeneous and its economic challenges easier to address. The description no longer fits the city as neatly, given its increased diversity, burdened education system, and neighborhoods increasingly segregated by class. "From what I see every day, we are in a real crisis right now," says Rosemarie Hunter, a social worker and the director of University Neighborhood Partners, a University of Utah outreach neighborhood program centered on low-income communities. "Not all, but of those some of the markers that gave us that great ranking have gone away."

For their part, Salt Lake City officials heralded the study as yet another piece of evidence for the region's high quality of life, alongside its low unemployment rate. But for another group of locals—social workers, educators, and community advocates—the study was also a cautionary tale.

Salt Lake City, with roughly 180,000 residents, shared the admirable distinction with major coastal cities such as San Diego, San Francisco, Seattle, Washington, D.C., New York, and Boston. The list generated significant buzz in academic, economic, and urban-planning circles both for its broad scope and for its finding that where people live can profoundly affect their children's economic futures. The U.S. is no longer uniformly the land of opportunity, the study showed, unless you happened to live in the right place.

In the summer of 2013, four prominent economists from Harvard and the University of California, Berkeley, named Salt Lake City one of the best places in the country for upward mobility. Low-income kids who grew up in the region, the researchers found, had some of the greatest chances of moving up the income ladder as they aged.

To maintain its status as a model for the American Dream, Salt Lake City government officials, civic leaders, and the powerful Mormon church are pursuing various strategies in schools and neighborhoods to try to continue to give lower-income children the best boost up the income ladder.

Salt Lake City still possesses two of the major strengths that made it one of the best cities in the country for upward mobility: a strong middle class and a less extreme gap between the rich and the poor. But what worries Salt Lake City academics and advocates now is that the city has fallen behind on other factors as it has become more global and diverse. "We're beginning to see the start of intergenerational poverty here, whereas we have not seen that in the past," says Pamela Perlich, a senior research economist with the local Bureau of Economic and Business Research. And that raises questions about whether Salt Lake City, like other rapidly changing urban areas, can continue to provide the best opportunities for its low-income kids.

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The Salt Lake City of the 1980s was a smaller town with a somewhat uniform population. Absent were many miles of bus routes and train tracks that link the city's public transportation system. The gleaming City Creek Center—a downtown shopping mall, housing complex, and mixed use development—had not yet been built by the deep-pocketed Church of Jesus Christ of Latter-day Saints along the city's central artery.

The population at the time was fairly homogeneous: white and Mormon. Families largely stayed intact, thanks to the cultural influence of the LDS Church and its emphasis on marriage. The Mormons' active social safety net system propped up the lives of any members in need. And even the public school system faced a relatively basic task, primarily educating native English-speaking, middle-class kids.

As it happens, the old Salt Lake City checked the boxes that the Harvard and Berkeley economists would later determine make a city achieve high rates of social mobility. In the 1980s and 1990s, the study showed that a low-income child in Salt Lake City had a 10.8 percent chance of rising up the income ladder to the top 20 percent. (San Jose boasted a higher probability of 12.9 percent, whereas the city of Charlotte provided its low-income kids with just a 4.4 percent chance.) The economists based the study on federal income-tax records of 40 million U.S. parents and their children, born between 1980 and 1982.

The study also identified five factors that can help to increase social mobility in different cities: less economic segregation, a good public school system, strong family stability, a reliable social safety net, and less income inequality. Areas with less urban sprawl and less racial segregation also performed better in the rankings, the researchers found.

That's why the raw data the researchers used for the study, from the 1980s and 1990s, vaulted Salt Lake City to the top of their list. The city of roughly 30 years ago boasted a good school system, hyper-strong social safety net, a strong middle class, and little segregation—economic or racial—because Salt Lake back then was so white, so middle class.

"Salt Lake City surprised me. I've never been there," says Hendren when asked about the list's composition. "The bottom of the list also surprised me. I've been to Memphis and Atlanta and would not have guessed those were some of the least mobile places in the U.S."

Yet many locals say the Salt Lake City of today can no longer claim many of those characteristics. The city does still boast a strong middle class and a greater percentage of its families remain intact compared to national figures. Salt Lake City also has some of the lowest rates of income inequality in the country, according to the Utah Foundation, a statewide public policy research group.

But a huge range of its other attributes have shifted. For one, it is no longer the case that the majority of Salt Lake City residents belong to the LDS Church, a cultural shift that distinguishes it from the rest of the state and means that fewer locals can take advantage of the church's welfare for its members. More than 50 percent of school-age children in Salt Lake City are minorities, with more than 100 languages spoken in students' homes in the River District alone. This has complicated the mission of the public education system, especially since Utah has the lowest school funding per pupil in the nation.

There's also greater geographical divide now between the well-off and low-income people. Any visitor can tell this just by driving along Interstate 15, the highway that cuts the city into two halves. The eastern portion has a demographic makeup similar to Vermont—white, well-off, home to the university campus, Statehouse, and downtown district of offices and restaurants. To the west of I-15 sits low-income neighborhoods that house the most recent influx of immigrants or refugees or low-income families. In one district on the West Side, as many as 90 percent of school kids qualify for free or reduced priced lunches.

The newfound poverty looks like this: On a recent Thursday afternoon, West Side residents lined up two hours in advance to pick up groceries from a local food pantry. Old, young, white, Hispanic, African-American, and disabled single people and families sat on wooden benches or stood in line, waiting for the truck to show up with the food.

Forty-four-year-old Peggy Pace started visiting the pantry about three months ago, when she could not pick up enough hours at her temporary job with the U.S. Postal Service to pay her rent and buy food. Her three grown children work blue-collar or minimum-wage jobs at UPS, an auto shop, and a retail store. They did manage to graduate from high school, unlike Pace—but she still does not believe any of them have leaped ahead to forge a more economically secure lives than hers. "I didn't feel like the kids had amazing opportunities here," she says, her bleached hair pulled back into a high ponytail.

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Figuring out a way to ensure that Salt Lake City's low-income kids can prosper and continue to move up the income ladder has become a bit of an obsession within the past two years among certain groups. Even the LDS Church, which reserves its robust charity for members, has joined the conversation. (With its international headquarters based in Salt Lake City, the church has a vested interest in the city's future.) "We know there are gaps now in community services for immigrants, or those in the community without a loud voice. We're trying to figure out how we, as an institution, can support those needs," says Rick Foster, the manager of humanitarian services for North America for the LDS Church.

The University of Utah started an outreach program more than a decade ago on the West Side to form partnerships with businesses, nonprofits, and schools to better serve low-income people. One program, the Westside Leadership Institute, trains residents to become more politically active in neighborhoods and to access decision makers. "Thirteen years ago, the university looked at its data and realized that two ZIP codes in the city had virtually no students coming to the university. That was a huge red flag," says Hunter of University Neighborhood Partners.

The Salt Lake City School District is also trying to address what its superintendent believes is a growing poverty problem. One strategy? Open a handful of community centers, like the Glendale-Mountain View Community Learning Center. Housed in a new $4.6 million building adjacent to an elementary and middle school, the center offers medical and dental care, mental health counseling, and classes to the roughly 6,000 people who live in the neighborhood.

"This state has a good network of taking care of people in need," says Natalie Gouchnour, the associate dean of the David Eccles School of Business at the University of Utah and chief economist and senior adviser to the Salt Lake Chamber of Commerce. "Part of that comes from the Mormon culture, but part of it is just the ethos of the state."

Still, there's no guarantee that these disparate experiments will preserve the city's overall level of social mobility. "There's not one good solution to all of these disparities across the U.S.," Hendren says. "We know that the quality of schools can matter as one example, but Americans still don't agree on the right policy to improve the schools."

Still, Salt Lake City's nonprofit leaders, educators, and academics feel optimistic. "We don't have intractable employment problems like Detroit or St. Louis, or the blight," says Perlich. Salt Lake City is also a small enough place, she adds, "with the tradition and wherewithal to do something." It's just a matter of whether everyone citywide (and on both sides of that highway) has the will and the resources to tackle the challenge.