The Metro East is a second auction with its own rules, not an extra zip code
The Illinois side of the river runs under a different state, which means different competitors, different costs and different licensing questions.
Give it its own campaign and its own budget. Mixing Belleville and Edwardsville clicks into a Missouri campaign hides what they cost and lets one side fund the other.
Send that traffic to a page that names the Illinois municipalities you actually work in. A landing page that only talks about St. Louis County tells an Edwardsville homeowner they are in the wrong place.
If you do not cross the Mississippi, exclude Illinois outright rather than relying on bid adjustments. Then check that your location settings target people present in your area, not people merely interested in it, because the default setting has funded a lot of out of state clicks.
Licensing and registration differ by state and by jurisdiction. Worth confirming with the relevant authority or your own counsel before you advertise work on either side.