In any given place, zoning laws decide what we can build and where. There are estimated to be some 30,000 local governments in the U.S. that employ zoning laws, and they can be complex. “Sometimes 150, 200, sometimes 3,000 pages that outline exactly what you can do in every lot in a city and connect those rules to corresponding maps,” said Sara Bronin at Cornell. “So zoning is text and map. And put those two together, and it really is the blueprint for how most places in the United States develop.”

Which might sound fine, but in many places, zoning laws have contributed to housing shortages. In Connecticut, for example, zoning laws have made it virtually impossible to build apartments or duplexes outside a select few areas.

And that’s where the Bronin and her team have come in. Bronin is director of the National Zoning Atlas, a federated effort to record and put all of the country’s zoning laws into one map, kind of like a Google map for land use regulation. While it’s very much a work-in-progress, the mapping tool was launched earlier this year.

“Marketplace” host Amy Scott spoke with Bronin about the National Zoning Atlas: how it came to be, and how it could be used to rethink zoning laws. The following is a transcript of their conversation.

Amy Scott: I think people’s eyes sometimes tend to glaze over when we talk about zoning. Not mine, I should say, I find it fascinating. But give us a sense of how important these laws are, that govern where and what we can build.

Sara Bronin: So zoning is this hidden power that governs, as you said, almost everything that gets built in this country. And each one of these local governments set out their own rules in massive texts, sometimes 150, 200, sometimes 3,000 pages that outline exactly what you can do in every lot in a city, and connect those rules to corresponding maps. So zoning is text and map and put those two together, and it really is the blueprint for how most places in the United States develop.

Scott: So what did you set out to do with this atlas?

Bronin: Well, the Atlas originated in Connecticut as part of an advocacy movement. The people who were involved in that understood that looking across a state with 180-plus different zoning jurisdictions, was hard for lay people. And if you didn’t understand how zoning worked, you couldn’t understand how to change it. Once we launched that Atlas, and it did, in fact, help lead to change, people in other states are using that methodology, which has evolved over time, to produce their own atlases.

Scott: All right, so we’ll talk about some of the changes that has prompted in a bit, but I want to get to know this tool. So I’m on zoning atlas.org. Let’s check out Connecticut. I’m going to open another tab here and zoom out a little bit so we can see the state. So what what do you see here?

Bronin: So Connecticut is a fairly small state when it comes to landmass. It has about 3 million people and it has about 183 zoning jurisdictions. Right now, you see across the state a sea of what would be the primarily residential color in the map, a sort of medium-purple color.

So when you go to “show me where people can build single family homes,” you’ll see the map change, but actually not by much. 91% of the state remains shown on the map in some shade of purple.

If you now click on apartments with four or more units, you will see virtually all of the purple disappear, leaving just about 2% of the land across the state zoned for multifamily housing. 

So now, when you go from overwhelming 91% of land allowing single family housing to underwhelming — or you can insert your own adjective here — amount of land in the state that allows for apartments, what does it say about a state that allows so little multifamily housing in its suburbs and rural areas? And puts all of it in the places where you can you would consider these the historic central cities? It doesn’t really seem like every part of the state is offering opportunities to a diverse range of households and people with lots of different preferences.

Scott: Wow. What impact has this mapping tool had? I mean, if a housing official or politician sees all that purple suddenly disappear to reflect that basically no apartments can be built in most of the state, has that changed anything?

Bronin: In Connecticut, the zoning atlas has informed change both at the state level and at the local level. So we have heard from advocates all over the state that they have used the atlas in their own communities at zoning board hearings, at city plan commission hearings. In addition, in other states, we’ve seen the Atlas tool used similarly for reform. In Montana and the Zoning Atlas that was created there, I think is probably a key example of that. There the Atlas helped to inform sweeping legislative changes that people have called the “Montana miracle.” And for me, no one’s going to read Baltimore’s zoning code of 569 pages. They might click on a map and they might say, “Oh, that’s, that’s interesting. Maybe we can do a little better.”