We provide evidence that the Norse were active on the North American continent in the year AD 1021. This date offers a secure juncture for late Viking chronology. More importantly, it acts as a new point-of-reference for European cognizance of the Americas, and the earliest known year by which human migration had encircled the planet. In addition, our research demonstrates the potential of the AD 993 anomaly in atmospheric 14C concentrations for pinpointing the ages of past migrations and cultural interactions. Together with other cosmic-ray events, this distinctive feature will allow for the exact dating of many other archaeological and environmental contexts.