The phosphate mines of central Florida, around Bartow and Mulberry, dig through a fossil bed so rich it is called Bone Valley: the dragline buckets turn up megalodon teeth and the bones of ice-age Florida by the ton along with the phosphate rock that fertilizes the world. Much of it is active private mine, but the Mulberry Phosphate Museum shows the finds and hands out free fossils, and some pits open for organized digs.
Fossils, phosphate
See it on the map
Other places on the map within a couple of hours.