I was recently reading the 1976 political science book Poliscide and part of Chapter 8 on the postwar zoning practices of DuPage County caught my attention:

Although no county can place guards at the county line to inspect the socioeconomic and racial characteristics of newcomers, such powers as zoning and control over subdivision and building codes make the county a highly effective arbiter of the types of structures to be built and, hence, the final arbiter of the types of people who will live in its jurisdiction.

For example, DuPage County enacts a subdivision ordinance requiring a developer to retain a large portion of his prospective subdivision for public facilities such as parks and schools; the county combines this with a zoning ordinance requiring single-family dwellings and a large minimum lot size. This effectively prohibits a developer from profitably building anything but high-cost housing not accessible to lower-income persons.

Stringent county building code standards, requiring expensive building materials and high-quality plumbing, wiring, and heating systems, also serve to increase housing costs. The county’s industrial zoning policy restricting heavy industry serves to limit job opportunity for lower-income persons and to prevent a decline in residential property values surrounding an industrial development – which might create housing opportunities for lower-income groups. Moreover, the county’s relations with various financial institutions make it difficult for a developer to secure financing for a project not approved by the county. Indeed, because of the obstacles the county is capable of placing in the path of a developer, the county’s objection may be sufficient to convince a financial institution that investment in a project would be unwise.

The county’s relations with other units of government give it yet another means of influencing the course of residential and industrial development. It is not, for example, an uncommon practice in Illinois for the county forest preserve district to condemn, at the count government’s behest, land on which an unwelcome development is planned…. And courts have made it a point not to intervene. If the acquisition was for a “public purpose,” there is no inclination to examine the underlying motives. (179-180)

And, as the political scientists point out, these were all legal procedures. Local governments, whether at the municipality, township, or county level, often have the power to dictate what can be built on the land over which they have jurisdiction.

At the same time, there have been court cases seeking to reverse these zoning powers. In 1971, DuPage County residents and a local fair-housing group brought suit against the county for exclusionary zoning practices. The Mount Laurel cases in New Jersey led to famous decisions suggesting municipalities cannot completely restrict cheaper housing (even if implementation has been messy).

More broadly, Sonia Hirt argues zoning in the United States serves one primary purpose: single-family homes. When wealthier suburbanites or urban dwellers get the opportunity to live in the homes they want or ones that have plenty of desirable traits, they tend to resist efforts to include cheaper housing nearby. (For a more recent urban case, see Portland.)

To some degree, the plan worked for a while in DuPage County. The authors of Poliscide say the county was the 3rd wealthiest in the nation, businesses were growing, and much of the development was relatively high-end. Yet, things changed over time. In the 2010 Census, DuPage County was the 62nd wealthiest county in the United States. (It would be interesting to analyze what role zoning played in vaulting all those other counties above DuPage County.) In the same census, the white along population was just over 70%. Some of this might be due to how the authors of Poliscide suggest municipalities fought back against the county: they moved to incorporate themselves as well as annex land so that they took over jurisdiction of land and DuPage County had less control over new development.