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is a city in Washington County, Missouri, United States. The population was 2,662 at the 2000 census. It is the county seat of Washington County. The city was founded in 1799 by Moses Austin and was named after the Bolivian silver-mining city of Potosí.
Potosi is located at (37.937881, -90.781932). According to the United States Census Bureau, the city has a total area of 2.2 square miles (5.6 km²), all of it land.