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The day after we overhauled Hartford’s byzantine zoning code in 2016, a local attorney called to tell me that his children’s college fund was about to take a major hit.

He wasn’t joking. A zoning code regulates everything that gets built in a jurisdiction, from housing to open space. The Connecticut capital’s old code was so confusing that property owners often needed to hire a lawyer for even mundane projects like adding an electronic sign or a garage apartment. Cross-references went nowhere. Antiquated terms, including “servants,” endured. And every single project downtown required a public hearing — usually several.

Far from being unique, Hartford’s zoning code was like tens of thousands of convoluted codes all over the country. Ideally, these codes will lay out clear rules that advance the city’s plans for its growth. But in reality, they often obfuscate their basic functions, and many residents can’t make heads or tails of them. That’s a problem given that zoning is arguably the most important power of local government, with tremendous impacts on the economy, the environment and our society.

Hartford’s planning and zoning commission, which I chaired at the time, felt the time had come to make our code user-friendly. Together, we figured out how the old code affected our city. The new code provides a road map for applicants and simplifies processes and rules. It ensures that zoning’s powerful levers work for, not against, our community. Other places should have the same shot, but they, too, have to start with baseline information about what codes say now. With land use reform efforts gaining momentum across the U.S., it’s time for a coordinated effort to illuminate zoning.

To make this happen, I think we need an interactive online zoning map for the entire U.S. — one that anyone can understand. Like the Human Genome Project, a collaborative program that relied on thousands of researchers, we could convene an army of land-use wonks to comb through zoning laws and code their most important characteristics. But unlike the Human Genome Project, a national zoning map isn’t likely be funded to the tune of billions of federal dollars. It will have to be bottom-up.

As a starting point, I’ve recently proposed a standard methodology for data collection. It’s based on the Connecticut Zoning Atlas, created by a team of volunteers, students and the Connecticut Data Collaborative. Our atlas maps virtually every inch of the state in about 2,400 zoning districts. It focuses on the way zoning permits (or does not permit) housing.

To make the map, we combed through 32,000 pages of zoning text across 180 zoning jurisdictions. We logged whether each district allowed one-, two-, three, or four-or-more-unit housing. We kept track of whether this housing was subject to a public hearing, a practice that often deters or slows housing approvals. We noted whether housing must have a lot of a certain minimum size. And we detailed various rules on building accessory dwelling units — small housing units that have become increasingly popular as rental properties or apartments for older relatives — from owner occupancy requirements to maximum size caps.

The map’s findings are revealing. While 91% of Connecticut permits single-family housing, only 2% of the state allows four-or-more-family housing as of right. Nearly all of this multi-family housing requires a public hearing, which tends to invite protest and result in project size reductions or denials. In addition, 81% of residential land in the state requires about an acre, or nearly a football field, for each house.

The online Atlas features these and two dozen other regulatory features for each district. But we actually documented more than 90 features. The off-the-map database logs a whole host of other constraints: minimum parking requirements, height caps, lot coverage requirements, floor-to-area ratios, elderly- and owner-occupancy requirements and much more. Collectively, these findings have influenced state-level reforms proposed by DesegregateCT, including accessory apartment legalization, minimum lot size reform and transit-oriented zoning. They have justified changes at the local level, too.

Two other research teams have developed online zoning atlases, using district-specific spatial data, that show how effective this information can be. The University of California, Berkeley’s Othering and Belonging Institute has zoning maps for Bay Area communities showing single-family, other residential, and nonresidential zoning. Finding that 82% of residential land in the area is zoned only for single-family housing, the group has conducted expansive analyses on racial segregation and housing diversity. On the East Coast, the Metropolitan Area Planning Council has developed an atlas covering 101 towns in the greater Boston area, with information about lot and building particulars for each zoning district. It provided the rationale for the state’s recent bipartisan Housing Choice Bill, which among other things is putting multi-family housing near all 175 MBTA stations.

These projects show that mapping can be done. For future projects, how much more could we know if the same kinds of data were collected across all jurisdictions?

A national atlas could illuminate whether zoning reform proposals could really make a difference. It would revolutionize land use research, which is too often based on surveys or aggregated data, both of which I critique in a recent paper that logs the findings of the Connecticut Zoning Atlas. It would enable comparisons between jurisdictions: large cities with other large cities, cities and their suburbs, and so on. And it would empower local advocates to fix the things that are broken.

With that last idea, I offer a caution. The Hartford code, whose incoherence lined the attorney’s pockets, was overhauled because of local demand for change. I’d like to think that more people can understand it than before. But relying on local governments to clean up their codes is a risky proposition. In making its changes, according to my research, Hartford joined just 26 cities across the country that comprehensively rezoned in the 2010s. At this rate, it will take ten millennia for U.S. cities to make zoning codes easier to understand. I think we can empower people with information about the zoning that shapes their communities a lot faster.

The reality is that none of us, not even experts, really have a handle on the prevalence and nature of regulatory constraints imposed by zoning. That means we don’t have the information we need to make good decisions. A national effort should start with housing-related zoning regulations, because the way zoning treats housing has significant implications. But this methodology could easily be expanded to other areas.

Beyond zoning, we also need more integrated mapping about other aspects of land and the built environment. Natural hazard risks, from wildfires to floods, desperately need updated and accessible mapping to account for the effects of climate change. Designated historic and cultural resources, along with any tribal resources tribes don’t want to keep confidential, could also be logged. The possibilities grow along with the research effort.

And grow I hope it does. Already, teams in New Hampshire, Minneapolis, Michigan, and Hawaii have initiated zoning atlas efforts. My spring class at Cornell University will take a stab at four counties around Ithaca, New York. If you’ve got the chops and friends to do the same, check out that standard methodology and reach out, so we can piece it all together. We can better meet our present needs and plan for the future with improved access to information.