The city of St. Louis stands apart from St. Louis County, which is split into dozens of small municipalities with their own names, school districts and loyalties. A homeowner in Ballwin, a patient in University City and a buyer in Affton all live in the St. Louis area, yet each tends to search with the name of the place they call home. When Google builds a local pack, proximity to that searcher weighs heavily, so a business sitting in Maplewood can be invisible to someone in Wildwood even though the drive between them is short.
Two states, one audience
The metro crosses the river into Illinois. Commuters from Collinsville, Granite City and Belleville cross the bridges every workday and search from phones on both sides. A company that serves those towns has to show it in its content, its service area settings and its citations, because a page that mentions only Missouri addresses tells the search engine very little about the Illinois half of its customer base.
St. Charles County adds another layer, with O'Fallon, St. Peters and Wentzville growing along the interstate west of the Missouri River. Each of these areas has searchers who expect results close to them, and each one deserves a deliberate decision: target it, or leave it alone.