Name the municipalities you serve in the first screen, not on a buried service area page
A visitor who cannot tell in three seconds whether you cover their address will go back to the search results and find someone who says it out loud.
The City of St. Louis is an independent city, legally separate from St. Louis County. Buyers here know that and sort themselves by it. A header that says "serving greater St. Louis" tells a Webster Groves homeowner nothing and tells a Belleville homeowner even less.
Put the actual coverage where it cannot be missed. Named municipalities, the counties you work in, and a plain statement about whether you cross the river into the Metro East. If you do not sell in Illinois, say that too. Turning someone away in the first screen is cheaper than turning them away on the phone.
Group the names the way locals do, city separate from county, with St. Charles County called out on its own. The grouping itself signals that you live here.
Then keep it honest. A coverage list padded with places you rarely drive to produces inquiries your schedule cannot serve, and those cost you twice.