Separation referendums in Illinois
Beginning in 2020, a number of counties of Illinois have held referendums relating to the separation of Cook County, and more specifically its city of Chicago, from the rest of Illinois. This might be achieved by splitting Chicago and some nearby areas off as a new state, separating themselves from Illinois to form a new state, or separating from Illinois and joining a neighboring state.
Source: Wikipedia — Separation referendums in Illinois (CC BY-SA 4.0)