St. Louis Region
Union has been Franklin County's seat since 1827
Union's role as Franklin County seat goes back to 1827, which explains why county offices sit there even when Washington or Sullivan may feel larger to a visitor.
Union is the place to look for Franklin County government because it has been the county seat for a long time. The State Historical Society of Missouri describes Union as the county seat on the Bourbeuse River and says it has held that role since 1827, after replacing Newport, also known as Dundee.
That history helps a modern reader. Washington, Sullivan, Pacific, and the I-44 corridor may be the places people know from errands or commuting, but county offices and public meetings still center on Union. If your task involves the assessor, collector, recorder, commission, court records, or Planning and Zoning, check the Union county-government path first.
References
Where this fits: this note belongs to Franklin County. See every local note for the county on its page.