The nations largest lead belt is the Viburnum Trend... This entire area was basically founded by early explorers tripping over lead.  The French explorers founded this area in 1720 because they found lead deposits on the ground near Old Mines Missouri. 90 percent of all the lead in the world is mined here.  Once an ancient sea, its uplifted floor untouched by scouring glaciers that stopped to the north.  Eons of erosion carved deep valleys into the Ozarks crusty limestone plateau, transforming its flat surface into the unlikely role of hills.  They march nearly level into the distance, and peak at 2,600 feet in Arkansas's Boston Mountains...  Ozarks region in Missouri and Arkansas by Randy Olson for National Geographic Magazine.