This Outer Side video unpacks one of America’s most striking geographic mysteries: why the eastern United States is carpeted with forests, while the west is home to vast deserts. It’s a dramatic contrast split across a single country, one shaped not by politics or borders, but by the power of nature itself, so why does U.S. have deserts in the west and forests in the east?
Picture warm, moisture-filled air drifting inland from the Atlantic Ocean and the Gulf of Mexico, feeding the green landscapes of the East. Forests flourish because rainfall is abundant. But as this same air mass pushes westward, it encounters a colossal barrier: the Rocky Mountains. And mountains, acting like towering walls, force moist air upward, wringing it dry as rain falls on their eastern slopes. What descends on the western side is parched, creating the massive rain shadow responsible for deserts from Nevada to Arizona and much of California.
Yet the story doesn’t end there, some coastal regions like Seattle and Portland still receive generous rainfall thanks to the Pacific Ocean. But even that isn’t enough to erase the deep climatic divide carved by the Rockies.
Join us as we explore how oceans, wind,
