Urbanist author and activist Jane Jacobs predicted the revival of cities, but didn’t think that extensively about the people who live in them. (Phil Stanziola/New York World-Telegram and the Sun Newspaper Photograph Collection/Library of Congress)

Emily Badger covered cities and urban policy for The Washington Post.

My copy of “The Death and Life of Great American Cities” is marked with stars and smiley faces in the margins. When I first read it in my mid-20s, I was ecstatic about discovering this woman, Jane Jacobs, who shared every one of my biases. Suburbs are monotonous and dull! Cars have strangled American cities! It’s so true, as she understood, genuinely good bookstores never open in newly constructed buildings.

The godmother of all urbanists has had this effect on 50 years of readers — city-dwellers whose radical ideas she helped legitimize. Jacobs gave voice, even moral and intellectual high ground, to a particular kind of nonconformist, the person who didn’t get the appeal of suburban malls or want the solitude of cul-de-sacs at a time when the American dream was reorienting around both. In the 1960s, she perceived order and value in what looked to others like urban decay. And she insisted that neighborhoods like her own Greenwich Village, with its aging buildings and busy sidewalks, embodied the vitality that suburbia could never possess. Her proposition was all the more remarkable because at the time, big American cities such as New York were shedding population and beginning a long decline. The suburbs were ascendent, and cities, to survive, were trying to copy them. Today, Jacobs’s counternarrative has become its own conventional wisdom (and many suburban town centers are now trying to mimic Greenwich Village).

But although Jacobs spent a lot of time pondering what could make urban economies succeed — the theme running across several of her books — she devoted much less attention to the possibility that success might create its own complications. And where she made us rethink the built material of cities — streets, buildings, blocks — she said little about the people who fill them.

Two new books tug Jacobs’s ideas into the 21st century — and explore what she missed — as her 1960s-era battles to keep highways and wrecking balls out of cities have been replaced by fears of the gentrification and inequality settling in. In “Eyes on the Street,” Robert Kanigel has written the definitive Jacobs biography, illuminating how her ideas rankled, spread and then garnered her such devotion. In “The Well-Tempered City,” developer Jonathan F.P. Rose loyally cites Jacobs but considers how cities must evolve in an interconnected and troubling world.

Kanigel appraises the work and life of Jacobs in prose that is as lively as her own. “Maybe you thought you didn’t want to march off to the suburbs like everyone else, that it was satisfying, or fun, or fascinating, to live amid a million strangers in an anonymous city,” he observes, “and here was a lady who thought so, too, who understood, and who helped you see your city, and maybe yourself, in a new and liberating way.”

It is a ripe moment for a new Jacobs biography, because the eccentrics she spoke for have now become culturally dominant. The new narrative says that Americans want to move back to cities. The kinds of dense neighborhoods Jacobs prized — near transit, heavy with foot traffic, their housing and commerce all jumbled together — now have the fastest-rising property values in the country.

Even in Detroit, according to census data, the white population is growing for the first time since 1950. In cities such as Washington, long-vacant plots of land have all been earmarked by developers. Bike lanes are proliferating (Jacobs was a bike commuter). If anyone is under siege, it’s the suburban commuter. The war on cities has become the war on cars.

But in this post-Jacobs world — she died in 2006 and would have turned 100 this year — her once-outlandish ideas feel both timeless and insufficient. She did not dwell much on the future of cities, a preoccupation of many authors today, given that she was writing in a time when their imperiled present was more urgent. Kanigel’s book invites the question of how this woman who forced so many of us to see cities differently might help us interpret their state today, and whether she’s up to that task.

Jacobs did not become a public intellectual until her late 40s, with the publication of “Death and Life,” making her an unlikely icon, a “pudding-faced old lady in ill-fitting jumper and sneakers.” She had no formal education in planning, economics or architecture, or even a college degree. But she elbowed her way among experts by staring more intently at problems others studied in the abstract. Among the many gems Kanigel unearths is this perfect reaction from the Wall Street Journal to her book “Death and Life”: “In another age, the author’s enormous intellectual temerity would have ensured her destruction as a witch.”

Kanigel’s story of how her ideas took hold is more interesting than her life itself (Jacobs always insisted she was quite ordinary). Even her fiercest critics were in awe of the woman, and the rightness that she claimed.

Time did, repeatedly, prove her right about both the value of cities and the threats to them. The highways she opposed were supposed to revive cities but helped speed their decline. The modernist public housing high-rises she disdained were dynamited in her lifetime. Monocultures, as she warned, did endanger whole economies, as happened when Detroit collapsed with its auto industry. Even transportation engineers eventually concurred: You can’t make traffic disappear simply by paving ever more lanes.

But where cities that followed her prescriptions have thrived, new problems have arisen. San Francisco’s booming economy has been accompanied by skyrocketing rents. Washington’s newly coveted “walkable” neighborhoods threaten to displace their longtime residents. Jacobs’s own Greenwich Village couldn’t accommodate today the working-class “sidewalk ballet” of baby carriages, fruit sellers, longshoremen and housewives she observed in the 1950s.

Jacobs is sometimes unfairly blamed for encouraging gentrification. If she helped fan the demand for neighborhoods like her own, she is not responsible for restricting the supply of such places, which is the real problem. For decades, while we overbuilt suburbia, we effectively stopped creating the kinds of neighborhoods Jacobs loved. But she did give us formulas for shaping lively streets and strong urban economies that don’t quite tell us how to resolve their side effects in 2016.

And she was remarkably mute about an urban problem of her time that we still live with today — what her editor called “the Negro question.” Jacobs wrote extensively about the importance of “diversity,” but she meant the diversity of uses in a neighborhood (offices, factories, restaurants, apartments), and the diversity of building types that allow those uses to coexist. Economic diversity may be implied in that picture, but racial diversity — or racial inequality — was never her subject.

Kanigel reveals a fascinating exchange of letters between Jacobs and her editor, Jason Epstein, in the weeks before she finished the manuscript for “Death and Life.” He begged her to tackle race, lest she publish an ambitious book on the problems of cities that said nothing of the particularly acute problems of blacks in cities.

“I don’t think that you can proceed as though the question didn’t exist,” Epstein wrote.

Jacobs responded, with the confidence that characterized all her other arguments, that this was “a poor idea for my book.”

Her view was narrow. She did not concede that others might value the kinds of neighborhoods she did not. And although she championed cities for people (as opposed to cities for cars, or bureaucrats, or master planners), she actually wrote little about the people in them. Repeatedly, critics accused her of overstating the power of physical environments over social context to shape us.

Despite its blind spots, “Death and Life” set a standard that urbanist authors have been nipping at since: the classic that alters how we understand cities, whose relevance could stretch across decades. And she left ample space for others to fill in. Economist Edward Glaeser’s 2011 “Triumph of the City” comes the closest of late to matching and complimenting Jacobs (Glaeser took her to task for enshrining old buildings that would, through historic preservation today, make it much harder to add new housing in expensive cities).

In his book, Rose, a longtime developer of affordable, mixed-income and green projects, picks up many of the topics Jacobs did not touch: income inequality, racial unrest, the hardship of growing up in poverty. And where she was certain about every one of her pronouncements, Rose has written a book that is largely about uncertainty: how cities will thrive in a “VUCA future,” using a military acronym for the simultaneous condition of volatility, uncertainty, complexity and ambiguity. Cities present wicked problems, he writes: “Every wicked problem is a symptom of another problem. And every intervention changes the problem and its context.”

Wicked problems have no clear solutions. Answers that help some wind up harming others. And so investments in poor neighborhoods invite gentrification. Economic growth exacerbates inequality. Rising property values (good for homeowners) mean unaffordable housing (bad for renters). Greater density (which could lower housing prices) taxes public transportation. Aggressive policing tactics that may make cities safer alienate the minority communities that bear the brunt of them.

This is a more useful frame for thinking about modern cities in which success is part of the challenge and threats come in more menacing forms than the hubris of Robert Moses, the New York master builder who devised much of the city’s earlier urban renewal. Today’s big cities, Rose points out looking across the globe, must also contend with population growth, climate change, resource depletion, widening inequality, refugee crises and terrorism. “The tide of megatrends is moving against our best intentions,” he warns, “and we are not working at a scale that is meeting the challenges of our times.”

Rose’s answer is a “well-tempered city,” a place where nature and man coexist in greater harmony, where every solution targets multiple problems at once (building weatherization creates jobs, cuts energy use, reduces housing costs and makes cities more resilient to disaster). In getting there, Rose tries to cover too much ground, from Mesopotamia to Freddie Gray, with too many overlapping analogies drawn from military jargon to musical theory to ecology. Where Jacobs had her sizable blinders, he wraps his arms around too much and draws too little on his own surely fascinating experience as a developer.

But his contribution is useful for defining the problems of cities in a world more complex than in Jacobs’s time.

The well-tempered city already exists, sort of. Imagine a city, Rose suggests, with Singapore’s social housing, Austin’s smart grid, Copenhagen’s biking culture, New York’s arts scene, Hong Kong’s subway, San Francisco’s recycling program, London’s congestion pricing and Tokyo’s public health. All these pieces haven’t come together in one place yet. If they ever do, that would be a modern ideal that would speak to more people than Jacobs’s 1950s Greenwich Village.

Eyes on the Street
The Life of Jane Jacobs

By Robert Kanigel

Knopf. 482 pp. $35

The Well-Tempered City
What Modern Science, Ancient Civilizations, and Human Nature Teach Us About the Future of Urban Life

By Jonathan F.P. Rose 463 pp. $29.99