Sue, the world’s biggest T-rex fossil, hails from South Dakota and in her time she wasn’t alone. The grasslands, badlands and mountains of western South Dakota are a treasure trove of ancient land and sea creatures. Thousands are buried here, and some of their remains still show up when heavy rain erodes sandy cliffs. On sunny days you can find fossils without getting your hands dirty. Try the Museum of Geology (free admission!) on the School of Mines campus in Rapid City. First-rate private museums also operate in Hill City and Hot Springs, and the latter is also home to the non-profit Mammoth Site, an in-progress excavation of a big sinkhole where many beasts became mired in mud 26,000 years ago. Most museums and rock shops in West River have at least a few fossils and petrified plants.