Books in the History and Genealogy Department are shelved in Dewey Decimal order. Knowing the Dewey Decimal number for a county or a series of counties within a state makes it easier for a researcher to browse the shelves. Clicking the links below will return charts listing counties in alphabetical order with their Dewey Decimal numbers.
Some St. Louis County Library call numbers begin with "R" ("Reference" materials that may used only in the library) or "Q". The Dewey Decimal Number proper begins after an initial "R" or "Q".