Planopedia

Euclidean zoning is the separation of land uses by type—residential, commercial, retail, industrial, etc.—each into their own zones or areas within a given city. While Euclidean zoning is frequently associated with the development patterns of suburbia, it's the most common form of zoning code, or the local legal tool for controlling the uses and development of land, in the United States. Even the largest cities in the United States have relied on Euclidean zoning throughout most of the 20th century and up to the present day.

The Euclidean moniker comes from the U.S. Supreme Court decision Euclid v. Ambler (1926). That decision granted local governments the power to determine which properties or zones in towns are most suitable for specific uses. The government that created the impetus for the court case, and thus a legal legacy that controls the use and development of land in almost every city in the United States: Euclid, Ohio.

Exclusionary zoning is another term frequently used to describe the separation of uses enabled by Euclidean zoning (i.e., single-family residential developments are allowed while multi-family residential, retail and commercial development are excluded), and sometimes the terms "exclusionary" and "Euclidean" are used interchangeably in public discussions about planning and zoning.

Another conceptual model helpful for understanding the separation of uses enabled by Euclidean zoning is a comparison between a "hierarchical model" of zoning compared to a "flat" model. In a hierarchical model, land uses are envisioned like a pyramid. At the bottom are industrial zones, where retail uses and residential uses are also allowed. At the top are residential zones, which only allow residential uses. A hierarchical model of zoning thus allows for some mixing in the kinds of zones located at the base of the pyramid. 

By comparison, in a flat model like Euclidean Zoning, each use is separated into its own area, allowing only one kind of use in each zone. In many communities, Euclidean zoning has been taken to the extreme by not only permitting only one kind of use in each zone, but also by excluding any potential variation on that use. Not only do most residential zones in cities exclude industrial and retail uses from residential neighborhoods, most residential zones also exclude variations among residences—i.e., houses are acceptable, but apartment buildings are not.

Euclidean zoning emerged and gained popularity for ostensibly humane purposes—easing the negative social effects of crowded tenements, for example, or mitigating the public health outcomes that occur when residences are located adjacent to highly polluting industries.

In recent decades, planners have become more aware of the negative environmental and social effects of Euclidean zoning. As Euclidean zoning spread communities out and forced local serving businesses out of residential neighborhoods, people became more and more dependent on automobiles for commutes and daily needs. Automobile dependency creates air pollution and congestion, and transportation is now the largest source of the emissions causing climate change in the United States. The exclusionary effects of Euclidean zoning have also been shown to cause housing discrimination and racial segregation. A 2011 study showed that the whitest, wealthiest neighborhoods in the country have some of the strictest applications of Euclidean zoning concepts. 

The growing knowledge of the negative effects of Euclidean zoning has inspired reform of traditional zoning practices and innovative new land use control systems. In some cases, zoning reform uses the traditional tools of Euclidean zoning, but with far less restrictive and exclusionary prescriptions. Mixed use zones, where new buildings are allowed more than one use, are one sign of zoning reform implemented as a response to the effects of Euclidean zoning. Other reforms take a more fundamental approach, like in the example of form-based codes.

Many forms of zoning reform, like mixed-use zoning and new forms of density, actually reinstate the ability to develop in the traditional forms and patterns that were prohibited when U.S. cities began to implement extreme variations of Euclidean zoning.