This historical anomaly is part and parcel of our grand post-World War II experiment in monocultural development—we now build whole neighborhoods conforming to a single template. We do it all at once, to a finished state, and then try to preserve the place under glass, never to change or evolve.

The legal vehicle for this approach is rigid, single-use zoning that segregates different land use patterns from each other. We’ve, in effect, replaced the diverse, complex ecosystem of a traditional neighborhood with the simple monoculture of a suburban subdivision: a place that is complicated (lots of rules and regulations) but lacks complexity.

And not only did we apply this paradigm to new postwar suburbs, but in city after city, especially in the 1950s through the 1970s, we downzoned neighborhoods that used to include the likes of duplexes, apartment buildings, and ADUs, and said "No more." This is how it came to be that my aunt could buy an old duplex in a neighborhood that bans new duplexes and live in it for 30 years.

Much has been written about why this shift occurred. In many places, racial politics was clearly part of it. Fear of neighborhood decline in an era that wasn't kind to inner cities motivated some downzonings. Apartments and renters became associated with decline, and so cities caved to homeowners demanding apartment bans in their neighborhood. In an insightful commentary on the subject, Slate’s Henry Grabar pointedly characterizes single-family zoning as an “apartment ban”—defined, in intent and effect, not by what it includes but by what it excludes.

But rigid, single-use zoning is also simply a part of the institutional mindset of the suburban experiment and the large-scale, corporate developers that have carried it out: efficiency and predictability require standardization, which requires monocultures. The heavy machinery used by a corn or soybean farmer to quickly till, water, and fertilize many acres is useless in a garden in which various species are interspersed. The mass-production model of the capital-D Developer is useless in an eclectic, mixed neighborhood.

The world mapped out by strict use-based zoning is all very orderly, and many individual homeowners have bought into the approach. You hear this focus on order in the way opponents of loosening zoning rules speak: “My home is my largest investment. The city owes me the certainty that the neighborhood around me won't change, in order to protect my investment.”

The problem? The real world is not so predictable or orderly. Economies change, employment patterns change, the population changes, and household composition changes (only 1 in 5 U.S. households is a nuclear family in a country built around single-family detached houses). A world built on fossil fuels is also finding that it, too, has to change. And so our neighborhoods must be allowed to change.

A Growing Sense of Crisis Motivates Diverse Advocates

There are more and more cracks in the facade of the suburban experiment. They look like crises that our landscape of homogenous single-family neighborhoods now stands in the way of addressing effectively. So whether your issue is climate change, or housing affordability, or racial justice and desegregation, or education reform, you're more likely than ever to have found common cause with the diverse coalition of groups pushing bills such as Oregon's HB 2001. The Sightline Institute's Michael Andersen describes that coalition in Oregon in this striking passage:

The issue has also scrambled partisan politics-as-usual. At the federal level, the Obama administration partially took up the cause of removing barriers to housing development, but so has the Trump administration. Issues such as racial desegregation or environmental justice are seen as liberal priorities, but HB 2001 transcended liberal politics, winning two-thirds of both the Democratic and Republican causes in the House, and passed the Senate by a 17-9 vote, including 14 of 18 Democrats and 3 of 8 Republicans. The bill's sponsor was a Portland Democrat, but a small-town Republican took up the mantle as well, as Andersen describes:

"We all have an affordable housing crisis in our areas,” said Rep. Jack Zika, a Redmond Republican who supported the bill before a different committee June 11. “This is not a silver bullet, but will address some of the things that all our constituents need. … We have an opportunity now for first-time homebuyers.”

Odd bedfellows, all reacting to very different facets of a common problem: rigidly exclusive single-family neighborhoods are a fragile way to plan cities that is inadequate to the challenges of a changing world.

Lessons From Oregon's Success

I spoke with Madeline Kovacs of the Sightline Institute, which has been on the forefront of "rabble-rousing" (her term) around housing affordability and other issues in the Pacific Northwest. Kovacs offered this measured take on the likely impact of HB 2001 in and of itself: