In his State of the State address, Governor JB Pritzker said he supports statewide zoning changes to promote more housing:

Gov. JB Pritzker will propose a statewide zoning law in his State of the State address on Wednesday, drastically limiting the authority local governments have to control what types of housing structures can be built on land that’s zoned residential…

A study published last year by the University of Illinois found that the state is about 142,000 units of housing short and would need to build 227,000 over the next five years to keep up with demand. That equals about 45,000 new homes a year — nearly double the five-year average of about 19,000 built annually between 2019 and 2024…

Pritzker’s office says the plan includes a tiered framework to permit multi-unit housing by right in all but the smallest lots zoned for residential use. Local zoning boards would no longer be allowed to prohibit property owners from building multi-unit housing on residential lots exceeding 2,500 square feet…06

More straightforward, accessory dwelling units — attached or detached secondary residences such as granny flats, backyard cottages and above-garage apartments — would be legalized on all properties zoned for residential use. The city of Chicago moved last year to relax its 60-year ban on granny flats. And legislation was filed in Springfield last year to ban local governments from prohibiting the units. But it has not moved.

Three thoughts in response to this proposal:

1. One feature Americans tend to like about suburbs and local governments is that they have control over land use decisions, not people located elsewhere. This means residents have more direct say about who might be there neighbor or what might be located next door. In roughly the last one hundred years, zoning in suburbs is then used to protect single-family homes and their values. Messing with this established use is not easy; as the article briefly notes: “the effort is likely to be met with stiff pushback.”
2. Illinois is not the first state to pursue this so there are other models to look at and see whether similar legislation has had positive effects. This has primarily occurred in blue states with more expensive housing markets than Illinois.
3. It will be interesting to see how different parts or communities in Illinois respond to this. The Chicago area housing market is different than downstate. How will wealthier suburban communities react? Which communities are most eager to construct affordable or missing-middle housing? Where would developers and builders want to construct housing if these statewide guidelines are passed?