The United States contains several regional ranges with color-based names. The Black Hills are geologically an ancient granitic dome in the Great Plains, famous for Mount Rushmore. The Blue Ridge Mountains (often called Blue Hills locally) are part of the larger Appalachian system in the eastern US, named for the bluish haze created by isoprene released from trees. The Green Mountains of Vermont are similarly part of the Appalachians. These ranges are geographically significant for their timber, mining history and role in defining the local topography and tourism of the American Northeast and Midwest.