Three buys, not one metro: the City, the county, and across the Mississippi
Split the account by geography first, because the offer, the ad copy and the landing page all change when the reader lives in a different state.
A campaign for the City of St. Louis, a campaign for St. Louis County and St. Charles County, and a campaign for the Metro East. Three separate budgets, three sets of ads, three landing pages. Anything less and you cannot see which of the three is paying for itself.
The split is not decorative. A reader in Edwardsville needs to know whether you take Illinois clients and what happens if a related state matter comes up. A reader in Kirkwood does not care about any of that. Same firm, different conversation, so the ad has to be different.
Check your location settings while you are in there. Most accounts run on the default that reaches people merely showing interest in an area, which is how a firm ends up paying for clicks from another country. Presence based targeting is usually the setting you want, and it is worth verifying in every campaign rather than assuming.
Budget the three separately, and be willing to switch one off. A campaign that cannot be evaluated alone is a campaign that will subsidize failure for a year.