Indian Springs Trace Fossil Natural Area in Fremont County, Colorado, is a 40-acre protected paleontological site on Indian Springs Ranch along the Gold Belt Byway. Designated a National Natural Landmark in 1980 and also protected under the Colorado Natural Areas Program, it preserves Ordovician trace fossils left about 450 million years ago in a tidal lagoon mudflat within the Harding Formation. Rather than bones or shells, the site records behavior: ancient animals walking, swimming, and burrowing. With 25 identified trace fossil types, including traces linked to horseshoe crabs, brachiopods, trilobites, and armor-plated fish, it is regarded as North America’s best trace fossil site.