During the nineteenth century, Americans were shocked to learn that the land beneath their feet had once been stalked by terrifying beasts. T. rex and Brontosaurus ruled the continent. North America was home to saber-toothed cats and woolly mammoths, great herds of camels and hippos, and sultry tropical forests now fossilized into massive coal seams. How the New World Became Old tells the extraordinary story of how Americans discovered that the New World was not just old - it was a place rooted in deep time.