Read more: Why are developers still building sprawl?

Despite being a city of 425,000 residents, Minneapolis until now has banned duplexes, triplexes, and larger apartment buildings from 70 percent of its residential land; in New York City, by comparison, just 15 percent of residential land is set aside for single-family homes. The city council’s Minneapolis 2040 plan up-zones the city to allow two- and three-family buildings on what had been single-family lots, tripling the potential number of housing units in the city.

Single-family zoning policies have an ugly history. In 1917, after the U.S. Supreme Court struck down policies that explicitly zoned separate residential areas for blacks and whites, many local governments shifted to a new form of exclusionary zoning: policies that banned the construction of anything other than single-family homes. These policies delivered many of the same results, by a different means—they kept out most black people and virtually all low-income people—but the Supreme Court upheld this new practice as legal.

Single-family zoning not only segregates people by race and class, but also artificially increases prices and hurts the environment. By outlawing the construction of duplexes, triplexes, and other multifamily units, single-family zoning artificially constrains the housing supply, driving up prices by government fiat. “When you have demand that is sky-high, and you don’t have the supply to keep up with it, prices rise. Rents rise,” noted Minneapolis’s mayor, Jacob Frey. Moreover, by artificially propping up housing prices and forcing families to move farther and farther out to find homes they can afford, single-family zoning puts more cars on the road for longer commutes, resulting in more greenhouse-gas emissions.

In the Minneapolis 2040 plan, the legalization of duplexes and triplexes was part of a package of reforms. The others included an increase in housing density near transit stops by allowing the construction of new three-to-six-story buildings; the elimination of off-street minimum parking requirements, which many experts view as a poison pill that makes the construction of low-cost housing economically unviable; “inclusionary zoning” rules that require new apartment developments to set aside 10 percent of units for moderate-income households; and $25 million in additional public funding for subsidized housing.

Predictably, the proposal to end single-family zoning and adopt other reforms triggered a major backlash from wealthy white homeowners. Critics called the elimination of single-family zoning a gift to developers, who would change the “character” of neighborhoods by overbuilding. Especially in wealthy Southwest Minneapolis, red signs bearing the slogan Don’t Bulldoze Our Neighborhood proliferated—even though no one was proposing to bulldoze anything. Several members of the Minneapolis city council voiced initial reservations about the plan. One said the proposal would be received “like a lead balloon” by his constituents.