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National Zoning Atlas Could Contribute to Zoning Law Reform, Policy Analysis

Published by Peter Lawrence on Thursday, August 10, 2023 - 12:00AM

The National Zoning Atlas project aims to create a tool that outlines different zoning codes by state in an online, user-friendly map, thus establishing the first ever compendium of local zoning regulations in the United States. The project’s overall goal is to make knowledge of local housing laws more available and digestible in order to revolutionize housing policy analysis and pave the way for zoning law reform. In a July article, the U.S. Department of Housing and Urban Development (HUD) highlighted efforts to advance the National Zoning Atlas project, placing a spotlight on the research of Sara Bronin, whose work has laid the foundation for a national atlas.

Bronin, a professor and researcher for Cornell University’s Department of City and Regional Planning, first unveiled the National Zoning Atlas project in May 2022. Thus far, the project has advanced most in states in the Northeast, which happen to be states with more stringent zoning laws, compared to the rest of the nation, as well as high housing prices overall. The Connecticut atlas, for example, depicts 2,620 zoning districts, which required a team to analyze, compile and map out over 32,378 pages of zoning regulations. Much of this work is driven by new advances in artificial intelligence (AI) that can compile and organize data faster than humans. In an article related to the latest update of Bronin’s work, she argues that zoning has been used to restrict access to certain jurisdictions, and thus access to opportunities, and limit the types of housing that can be built.

Zoning has always been considered a local issue, but Bronin believes that a nationwide database, that digitizes state zoning information will make it easier to make plain the negative effects of zoning she outlines when discussing the project, and hopefully spur change. This has already happened in Montana, where, once that state’s zoning atlas went live this year, numerous housing bills were introduced and passed due to the collaborative efforts of researchers with the Montana Zoning Atlas, a statewide housing task force and legislators.      

Background on the Atlas

The idea of a National Zoning Atlas was born in a 2021 paper by Bronin titled Zoning by a Thousand Cuts, in which she called for a national zoning atlas in order to better and more easily illustrate the scope and effects of the patchwork regime of restrictive zoning laws across the country. The project consists of more than 20 teams across the country working in 24 states. Cornell University collaborates with an expansive network of universities and nonprofits from all 24 participating states, such as Open Philanthropy and the Mercatus Center at George Mason University, to develop the atlas and the technology behind it. The project also obtained the vital assistance of grant funding government agencies such as the National Science Foundation and HUD’s Community Development Community Block Grant Disaster Recovery Program.

In addition to mapping zoning codes nationwide, the project also seeks to streamline the terminology and language that varies from state to state and between localities. However, according to Bronin, there remain technical challenges that need to be overcome through the development of the atlas. There are machine learning issues with the atlas due to having to comb through dense and complicated text, as well as issues parsing through cross-references and tables. Human review processes are necessary to account for unintended analytical processes and to correct the AI learning process in the case of systemic errors or bias.

Blog Graphic: States With Zoning Atlas Projects Underway

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Despite Difficulties, Zoning Atlases are Causing Change  

Although a multitude of teams from around the country are working on the project, there are only three complete state zoning atlases–Connecticut, New Hampshire and Montana. The Connecticut atlas was the first to be developed and completed and, as noted above, was a massive undertaking.. This is in sharp contrast to New Hampshire, which has fewer and larger housing districts, numbering 269 in total, with the state zoning atlas proving valuable in delineating between municipal, sub-municipal and independent and unincorporated zoning authorities. The Montana zoning atlas uses the standardized methodology established by the National Zoning Atlas programs to initially evaluate 13 fast growing Montana counties to analyze local zoning regulations, later expanding the project to cover the whole state. The Montana researchers argue that the atlas illustrates that overly restrictive zoning laws have inhibited development of multifamily dwellings in Montana.  

The Federal Standard Zoning Enabling Act, which introduced zoning laws into the United States in 1922, has not been updated since the its implementation, so there has been little movement towards zoning reform on the federal level. However, on the state level, the atlas project is already spurring policy change and enhanced policy analysis. In Montana, the state atlas project and the support of its sponsor, the Frontier Institute, helped spur a slew of housing reforms passed in April which loosened zoning laws regarding duplexes and accessory dwelling units and limited parking requirements. The Minnesota Zoning Atlas is currently underway, and the move in 2018 to eliminate single family zoning in Minneapolis–at the time single-family zoning made up 70% of total land area in the city–will undoubtedly serve as an example for other cities in the state to replicate. The Connecticut state atlas project was used to determine that 90.6% of zoned land in the state allowed single family houses to be built by-right (without special permitting or hearings) while conversely, only 2.1% of zoned land in the state allowed four-or-more family housing to be built by-right. In New Hampshire, the state atlas project determined that by-right building of duplexes was limited to 9.7% of buildable land area, and 8.3% for developments that can house five or more families, being significantly less restrictive than its neighbor Connecticut.

Addressing Zoning Challenges Can Have Wide-ranging Benefits

One instance of the barriers created by zoning is the example of Westchester County, New York. Two communities within the county, the wealthy and majority-white Scarsdale and the poor and majority-Hispanic Port Chester exhibit vastly divergent socio-economic demographics, with 0% of elementary-level students in Scarsdale reported as eligible for free or reduced school lunches–which means that none of the students’ families earn incomes at or below 185% of the poverty line–while in Port Chester, more than 75% were reported as eligible as they come from households making less than 185% of the poverty line. More broadly, the median household income in Scarsdale was more than $250,000, compared to Port Chester, where it was $88,903.

Many of the disparities between the neighboring cities are exacerbated by their differing zoning laws, in particular, those regarding multifamily housing construction. Westchester county directed much of its federal funding for multifamily construction in Port Chester and directed zoning laws to foster multifamily housing development there, all the while restricting it in Scarsdale in favor of single-family homes. Using Westchester County as an example, it can be seen that zoning laws have thus served to restrict economic development and preserved patterns of racial segregation and unequal economic and educational outcomes.

Zoning policy is important not only for the purposes of developing more housing, but it also affects racial segregation. Zoning law reform is seen as a key mechanism to removing many barriers to access to housing as well as access to economic and educational opportunities; there has been a recent uptick in efforts to remove these barriers. Notably, California eliminated exclusive single-family housing in September 2021, after four years of previous attempts to do so. As a result, their cities were more likely to change their zoning laws in 2021 compared to seven years prior, with California cities committing to more than 500,000 units of rezonings, a tenfold increase from 2014. New housing was also found to have been built more equitably across communities, with housing targets dramatically increasing in higher-income areas such as Beverly Hills after the reforms passed. More broadly, zoning reform efforts seen in National Zoning Atlas states have reported increased momentum behind legislative efforts on the state level to reform and loosen zoning laws. However, progress on zoning reform remains slow and limited to a state-by state basis.


The need for zoning reform has not escaped legislators. The Senate version of the Affordable Housing Credit Improvement Act, S. 1557, introduced in May, includes a Sense of the Senate resolution addressing land use and zoning policy.  Also in May, Sens. Todd Young, R-Indiana, and Brian Schatz, D-Hawaii, reintroduced the Yes In My Backyard (YIMBY) Act, S. 1688, which is designed to spotlight discriminatory land zoning policies, encourage localities to cut burdensome regulations and bring a new level of transparency to the community development process. In addition to legislation, on July 27, HUD and the White House announced efforts to protect renters, lower housing costs and boost the housing supply. One of HUD’s initiatives is the Pathways to Removing Obstacles to Housing (PRO Housing), which provides $85 million in competitive grants to encourage state and local governments to relax zoning restrictions.

The National Zoning Atlas Project, with its analysis of the many thousands of individual zoning policies across the country, allows for policymakers and advocacy groups to further analyze the breadth and depth of zoning laws. This analysis can lead to changing zoning laws to allow for increased multi-family housing production, increased investment in distressed areas and an erosion of the racial barriers surrounding housing. The project remains an important, and steadily growing tool for zoning policy analysis and reform and can only grow stronger as more states are added to the atlas over time. The development of the National Zoning Atlas represents a significant commitment to reforming zoning laws in general as well as analyzing their effects on distressed and disadvantaged areas across the country.

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