Minneapolis will become the first major U.S. city to end single-family home zoning, a policy that has done as much as any to entrench segregation, high housing costs, and sprawl as the American urban paradigm over the past century.

On Friday, the City Council passed Minneapolis 2040, a comprehensive plan to permit three-family homes in the city’s residential neighborhoods, abolish parking minimums for all new construction, and allow high-density buildings along transit corridors.

“Large swaths of our city are exclusively zoned for single-family homes, so unless you have the ability to build a very large home on a very large lot, you can’t live in the neighborhood,” Minneapolis Mayor Jacob Frey told me this week. Single-family home zoning was devised as a legal way to keep black Americans and other minorities from moving into certain neighborhoods, and it still functions as an effective barrier today. Abolishing restrictive zoning, the mayor said, was part of a general consensus that the city ought to begin to mend the damage wrought in pursuit of segregation. Human diversity—which nearly everyone in this staunchly liberal city would say is a good thing—only goes as far as the housing stock.

It may be as long as a year before Minneapolis zoning regulations and building codes reflect what’s outlined in the 481-page plan, which was crafted by city planners. Still, its passage makes the 422,000-person city, part of the Twin Cities region, one of the rare U.S. metropolises to publicly confront the racist roots of single-family zoning—and try to address the issue.

“A lot of research has been done on the history that’s led us to this point,” said Cam Gordon, a city councilman who represents the Second Ward, which includes the University of Minnesota’s flagship campus. “That history helped people realize that the way the city is set up right now is based on this government-endorsed and sanctioned racist system.” Easing the plan’s path to approval, he said, was the fact that modest single-family homes in appreciating neighborhoods were already making way for McMansions. Why not allow someone to build three units in the same-size building? (Requirements on height, yard space, and permeable surface remain unchanged in those areas.)

The U.S. Supreme Court struck down race-based zoning in 1917, but nine years later, found it constitutional for a Cleveland suburb to ban apartment buildings. The idea that you could legislate out not just gritty industrial facilities but also renters spread rapidly. In concert with racism in real estate, police departments, and housing finance, single-family zoning proved as effective at segregating northern neighborhoods (and their schools) as Jim Crow laws had in the South.

Opening up Minneapolis’ wealthiest, most exclusive districts to triplexes, the theory goes, will create new opportunities for people to move for schools or a job, provide a way for aging residents to downsize without leaving their neighborhoods, help ease the affordability crunch citywide, and stem the displacement of lower-income residents in gentrifying areas. Homeownership in Minneapolis diverges along racial lines, with minority groups’ rates lagging between 20 and 35 percentage points behind that of whites. More rental supply citywide, in addition to a new $40 million slice of the budget for affordable housing, is expected to help tenants find a foothold. The mayor, for what it’s worth, is a renter himself—maybe the first tenant-mayor in the history of a city where (like in most American cities) the majority of people live in rental housing.

City Council President Lisa Bender says the plan didn’t require a huge leap of faith. The city had already permitted accessory dwelling units. It had already loosened parking requirements near transit. And then, too, there’s the living history of a Minneapolis that grew before single-family zoning. “Our city originally developed along streetcar lines, so we have many neighborhoods that have a rich diversity of housing type and land uses, including duplexes, triplexes, and smaller multi-family buildings,” she said. “So we were able to keep pointing back at those neighborhoods and say, ‘This is a pretty incremental change.’ ”

Human diversity—which nearly everyone in this staunchly liberal city would say is a good thing—only goes as far as the housing stock.

Obviously, not everyone agreed. Residents submitted 7,000 comments on the draft plan, which was released in March. The initial proposal to permit four-unit buildings citywide was pared down to triplexes. (A last-minute plan to bring that down to duplexes failed in November.) A lawsuit brought by two birding groups and a brand-new organization (misleadingly) called “Smart Growth Minneapolis” threatened to halt the vote at the last minute, before a judge ruled on Thursday it could proceed. “This is a revolutionary approach to the zoning process,” explained Jack Perry, a lawyer for the plaintiffs who tried to halt the plan’s passage. “They’re getting rid of all R1 and R2 low-density zoning, and I think everyone has accepted this as the most ambitious upzoning proposal anywhere in the U.S. by far.” Unfortunately for the plaintiffs, comprehensive plans in Minnesota are explicitly immune from environmental review.

The claim of that lawsuit—that a denser, more populous city might be an environmental hazard and should require environmental review—will sound familiar to pro-growth advocates in California. There, local NIMBYism has pushed housing demand into the desert, lengthening commutes and helping to turn transportation into the state’s largest contributor to greenhouse gas emissions.

In Minneapolis, however, environmentalism was largely seen by officials as an argument in favor of the plan. “There’s this obsession with the color green,” observed Nick Magrino, who sits on the city’s planning commission. “People say, ‘My lawn is going to go, and that has green in it!’ You’re either going to get three units there, or three units distributed on torn-up wetland. It seems like at best a misunderstanding of how ecological systems work, and at worse a bad-faith plan.” An earlier reduction in required parking has already produced more “missing-middle” housing, he said, including market-rate studios starting below $1,000 a month. The new plan should only further that trend.

Several things made this possible in Minneapolis, observed Paula Pentel, coordinator of the University of Minnesota’s urban studies program. First was the election of a very progressive city council dedicated to making room for more housing in the city. Second was the emergence of various activist groups who came out to community meetings, put up lawn signs, and generally voiced their support for reforming the system wholesale. Third was the city’s extensive years-long effort to make sure public outreach didn’t involve only the usual suspects. Instead of waiting for residents to come to planning meetings, planners found residents where they were—at weekend street festivals, for example.

Did anyone change their mind? That’s not clear. But, Magrino says, the stake of single-family homeowners isn’t so high. Nobody’s losing their house. Nobody’s losing their lawn. Someone might, at some point, lose their parking space—but by then, the hope is, there will be plenty of stuff within walking distance.