Bonne Terre, named for the lead-bearing "good earth" of the area, lies in the oldest and largest mining district of Missouri, the leading lead producing state in the U.S. since 1908. Missouri's lead was the basis of its first permanent settlement and major industry. Lead, long used by Indians and known to French gold and silver seekers of the early 1700's, was not seriously mined until the failure of John Law's "Mississippi Scheme" showed that there was no gold or silver in the area. After the "Mississippi Bubble" burst in 1720, Philip Renault, an employee of the French Company of the Indies, opened lead diggings in this Lead Belt region of Missouri. Jean Baptiste Pratte operated the first lead diggings at Bonne Terre in the late 1790's. In 1864, the New York chartered St. Joseph Lead Company bought the 946-acre Pratte lead diggings, then owned by Anthony La Grave, for $75,000. With early use of the diamond drill in prospecting and with rich lead deposits, the company became the nation's top lead producer. Bonne Terre was long a mining settlement and was laid out by the St. Joseph Lead Co. in 1880. It is one of many closely spaced St. Francois County mining towns in the largest lead district in the U.S., including Desloge, laid out by Firmin Desloge in 1877, and Flat River, the scene of a mining boom in the 1890's and laid out in 1913. The first Americans in this area settled Spanish land grants on nearby Big River in 1794, and Murphy's Settlement, now Farmington, was established to the south in 1801, where Sarah Barton Murphy started the first Sunday School west of the Mississippi about 1807. When St. Francois County was organized in 1821, Farmington became the county seat. Much of St. Francois County lies in the geologic center of the Ozarks, the oldest of U.S. mountain regions. Its enormous chat piles attest the county's mineral wealth, where galena, or lead sulfide, is mined in massive man-made caverns from dolomite deposits measuring up to 600 feet. In southwest St. Francois County is Iron Mountain, the scene of a great iron mining boom of the mid-1800's.