Several border cities in the Midwestern United States are this way.
From the map at https://kchistory.org/faq/why-there-kansas-city-both-kansas-and-missouri, it looks like ~90% of Kansas City is in Missouri:-) (I dunno about differential population density though)
And in the same state a good portion of the greater city area surrounding St. Louis lies in Illinois (https://en.m.wikipedia.org/wiki/St._Louis)
The area around Chicago - TIL it is called “Chicagoland”, can anyone comment how often that is used by people in the region? - likewise extends into multiple (more than just two) states!
can anyone comment how often that is used by people in the region?
Frequently, though it’s mostly informal shorthand for “the greater Chicago metropolitan area”, you probably wouldn’t say “I live in Chicagoland” unless you were intentionally being vague.
Not in front of people from ACTUAL Chicago. They’re REALLY touchy about that afair…