Charles le Moyne de Longueuil, Baron de Longueuil was travelling through the area with French troops in 1739 trying to track and defeat the Chickasaws.  Some of his men found several bones that looked like they came from an elephant.  Longueuil had his men carry the large bones including a huge molar (mastodon tooth) out.  The fossils were later sent to Paris where Georges Cuvier discovered them and worked on them.  It was one of the artifacts that he used to show that fossils were from now extinct creatures.  

Later Thomas Jefferson sent William Clark in 1807 to collect from the site.  The salt lick appears to have attracted animals which then became entrapped in the swamps.  

Big Bone Lick State Park

Big Bone Lick State Park is located at Big Bone in Boone County, Kentucky. It is located on Beaver Road and between the communities of Beaverlick and Rabbit Hash. The name of the park comes from the Pleistocene megafauna fossils found there. Mammoths are believed to have been drawn to this location by a salt lick deposited around sulphur springs. Ancestors of the sloth, bison, and horse^[6] also grazed the vegetation and salty earth around the springs that the animals relied on for their diet. The area near the springs was very soft and marshy causing many animals to become stuck with no way to escape.^[1] It bills itself as "the birthplace of American paleontology," a term which dates from the 1807 expedition by William Clark undertaken at the direction of President Thomas Jefferson.^[7]

• http://en.wikipedia.org/wiki/Big Bone Lick State Park
• Page 25 - Kolbert, E., 2014, The Sixth Extinction: An Unnatural History: Henry Holt & Company, New York, 319p.