The world's most famous dinosaur -- "Sue," the gigantic T-rex at Chicago's Field Museum -- was discovered in South Dakota. Our Badlands National Park contains some of the world's richest Oligocene fossil beds, and archaeological sites across the state offer clues about early societies. While Hot Springs, S.D. is home to the Mammoth Site where researchers have found over 105 mammoth tusks, accounting for at least 55 mammoths. This was apparently the site of an ancient spring-fed sinkhole.