(Missouri) "Mine a Burton, March 23", manuscript postmark with matching "10" rating on folded letter datelined "Washington March 23, 1814" to William Clark, the Governor of Missouri Territory at St. Louis, Very Fine. Estimate  $600 - 800. THIS IS THE ONLY RECORDED COVER USED FROM THE MINE AU BRETON POST OFFICE. Mine au Breton was founded by Moses Austin on his land grant from the Spanish government in 1797. It was named for Francis Breton, who had discovered lead ore outcroppings there about 1760. In 1812, the adjoining town of Potosi became the county seat and Mine au Breton was gradually swallowed up by the new town. The post office was established in 1811. For some inexplicable reason, the postmaster wrote the town name as Mine au Burton.William Clark was the youngest brother of George Rogers Clark. He was co-leader, with Meriwether Lewis, of the Lewis and Clark Expedition. In 1807, he was appointed Brigadier General for the Territory of Louisiana and in 1813 was appointed Governor of Missouri Territory, retaining that office until Missouri became a state in 1821. In 1822, he was made Superintendent of Indian Affairs in St. Louis and served in that capacity until his death in 1838. $0 (Image)