Washington County, Missouri was organized August 21, 1813 from Ste. Genevieve County. The County Seat is Potosi, Missouri, 63664.
Frenchmen RENAULT and LaMOTTE toured the area near present-day Potosi in 1722-23. No permanent settlement was made until 1763, when Francis BRETON settled near Potosi and began to operate a mine bearing his name. The Bellview Valley, near Caledonia, was settled in 1802 by Annanias McCOY, Benjamin CROW, and Robert REED.
Washington County is divided into eleven Townships: