Cambridge, Massachusetts, enacted reforms last month that overturn century-old zoning regulations long embedded in American land-use practice. By establishing a generous citywide baseline for housing development—a standard that permits more housing across the city—the reforms replace a system that entrenched the status quo with one that embraces growth. Cambridge has set itself on a more welcoming course that other cities across the country can follow.
As Sonia Hirt described in her book, Zoned in the USA, the United States originated single-family zoning, an approach largely unknown in most other countries. Instead of simply regulating residential buildings by height or floor area, American zoning added strict limits on the number of dwelling units allowed in each structure. Local governments created a patchwork of residential zones, each carefully fitted to neighborhoods in the manner of a private covenant.
What this had to do with property rights or a city’s authority to regulate health and safety was unclear. How could a three-family home be legal and safe in one part of the city, but not in an adjacent neighborhood, especially when each had access to the same municipal services?
In Cambridge, zoning by dwelling unit count began in 1924, when the city’s first zoning code introduced four residential zones. The most restrictive allowed only duplexes, with a two-and-a-half-story height limit. Over the next 40 years, the city steadily tightened restrictions: in 1943, a revised code introduced single-family zoning and minimum lot sizes; in 1962, minimum parking requirements and floor area ratios were added. Overlay zones proliferated in the decades that followed. By 2024, the number of distinct zones in Cambridge had grown from 12 in 1924 to 53—a dramatic expansion of regulatory complexity over a century.
What did these accumulated restrictions produce? Cambridge’s formerly robust growth slowed and even reversed. In the 50 years between 1930 and 1980, the city’s population fell from 113,643 to 95,322 and recovered only gradually thereafter. By the twenty-first century, building taller and denser residential buildings was nearly impossible in most of the city. Cambridge city councilors have estimated that 85 percent of all residential units in the city did not conform to the zoning code.
Now, the city’s 2025 reforms sweep away this legacy of bad planning ideas. Gone for all residential zones are the minimum parking requirements and floor-area ratios from the 1962 code; the minimum lot-size requirements and single-family zoning from 1943 code; and even the concept of severely limiting the number of units per building fundamental to the 1924 code, and to American zoning practice generally.
Some cities have claimed to abolish single-family zoning, but if that change merely shifts to duplex zoning, it is a difference of degree, not of kind. Other cities have allowed greater density but confined those reforms to corridors or select areas, leaving most single-family zones untouched. Cambridge’s reforms, by contrast, represent a wholesale rejection not only of the principles behind its own first zoning code but also of American residential zoning practices dating back to the 1910s and 1920s. In their citywide application, acceptance of denser development, and rejection of zoning as a stand-in for private covenants, Cambridge’s reforms represent a fundamentally new approach to residential land use.
Not all zoning has been unwound, of course. Restrictions on nonresidential uses remain, and the city has implemented inclusionary zoning for developments of over a certain height, or a certain number of units; these are directed at social and economic concerns and not health and safety. Too many zoning districts remain. Height restrictions, which predated zoning in the United States, have been liberalized but not abolished. Still, few if any other cities have challenged the fundamental elements of American residential zoning practice so directly.
A century under that system has yielded a housing shortage that stresses Americans’ finances and limits their mobility. Cambridge’s city council deserves credit for showing other cities the way to a new approach.
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