Southeast Missouri / Lead Belt / Mississippi Corridor
Potosi: why the county seat sits where it does
Potosi is the county seat and the home of the courthouse and county offices, and its location is tied to the early mining settlement that started the county.
Potosi is the county seat of Washington County. A county seat is the town where the main county government sits. Potosi has the courthouse and most county offices. So when you need to handle county business, you usually go to Potosi. That includes things like your property assessment (the value put on your land for taxes), paying taxes, or recording documents.
Why is the seat in Potosi? The town started as an old lead-mining settlement called Mine au Breton. The county grew up around that early center. Today, county paperwork goes through Potosi, not the town closest to you.
Office hours and locations can change. So check the Washington County government website before you go. For history questions, you can ask the State Historical Society of Missouri or the Missouri Secretary of State.
References
More from Washington County: browse every local note for the county.
Last checked against the sources above: June 15, 2026.