These studies, and similar findings, tap into a broader worry. When a city grows rich, its wealth tends to outpace its housing supply, forcing prices higher and making vast swaths of the city unaffordable for middle-class families. And once the rich are ensconced, they typically resist the development of more housing, especially low-income housing, anywhere in their vicinity. In America’s 100 biggest metro areas, six in 10 homes are considered “within reach” of the middle class. But in the 20 richest cities, fewer than half are.

Only three large metros where at least half the homes are within reach for young middle-class families also finish in the top 10 in the Harvard-Berkeley mobility study: Salt Lake City, Pittsburgh, and Minneapolis–St. Paul. The last is particularly remarkable. The Minneapolis–St. Paul metro area is richer by median household income than Pittsburgh or Salt Lake City (or New York, or Chicago, or Los Angeles). Among residents under 35, the Twin Cities place in the top 10 for highest college-graduation rate, highest median earnings, and lowest poverty rate, according to the most recent census figures. And yet, according to the Center for Housing Policy, low-income families can rent a home and commute to work more affordably in Minneapolis–St. Paul than in all but one other major metro area (Washington, D.C.). Perhaps most impressive, the Twin Cities have the highest employment rate for 18-to-34-year-olds in the country.

What’s wrong with American cities? is a question that demographers and economists have debated for years. But maybe we should be looking to a luminary exception and asking the opposite question: What’s right with Minneapolis?

In the mid-1800s, companies that included the forerunners of Pillsbury and General Mills sprang up along the Saint Anthony Falls, the only major waterfall on the Mississippi River, in the center of Minneapolis. They saw in its cascade the ideal setting for water-powered mills. But when they tried to tunnel under the bedrock in 1869, the limestone collapsed, altering the falls. Thanks to a giant engineering project led by the Army Corps of Engineers, the falls were permanently restored in 1885. Although it hardly matches the sublime natural drama captured by 19th-century painters, the Minneapolis landmark still flows, rarely floods, and never breaks.

Myron Orfield, the director of the Institute on Metropolitan Opportunity at the University of Minnesota, recently described to me this short but perfect waterfall, “the ideal size for milling,” and I couldn’t help but think that the Saint Anthony Falls were a metaphor for the city’s advantages: a blend of geographical blessings and thoughtful city planning—all of which, to an outsider, looks deceptively boring.