Colorado and Rocky Mountains
Snow slowly fades from the peaks of the Rocky Mountains in the US Midwest and Colorado, shown here in this true-color Terra MODIS image from June 19, 2005. The Rocky Mountains are a collection of smaller ranges that stretch from British Columbia in Canada all the way into New Mexico (though some say that they extend as far north as Alaska and as far south as central Mexico), as well as a literal and metaphorical boundary between the US Midwest and West. They form part of the continental divide - i.e., the point at which water either drains toward the west into the Pacific Ocean or to the east into the Arctic and Atlantic oceans. These mountains formed at least 300 million years ago, and have been home to humans since the last great Ice Age.
This image shows a number of US states - Colorado in whole, and eight surrounding. At upper left is Wyoming; clockwise around the edge of the image are Nebraska, Kansas, Oklahoma, New Mexico, Arizona, and Utah. Starting as a watershed from the Rockies and moving east through the image is the Arkansas River.