The Americas are a large landmass containing the continents of North America and South America. They are connected by the narrow isthmus of Panama. The Americas are the second largest contiguous landmass on Earth, after Afro-Eurasia. The largest nation in the Americas by area is Canada, and by population is the United States. The Americas were populated by nomadic hunter-gatherers who crossed the Bering land bridge from Siberia. After the end of the last Ice Age approximately 11,000 years ago, these inhabitants were isolated from the rest of the world until 1492, when Christopher Columbus initiated long-term contact between the Americas and Europe.