The Bighorn Basin in northwest Wyoming contains both Early and Late Cretaceous rocks that were formed in rivers and floodplains bordering a sea that covered much of the central United States over 45 million years (from 110 to 65 million years ago). These rocks often contain fossils of dinosaurs that roamed North America during this time. Join Field Museum scientists as they explore this area in search of dinosaurs.\n\nExpedition Site\n