A mountain range is a series of connected mountains considered as a single system because of geographical proximity or common geologic origin. Mountains are considered to have a common geologic origin if they formed at
the same time by the same set of geologic events. Throughout history, mountains have acted as barriers for trade and conquest. Traditionally people who lived in the mountains tended to be isolated from other groups and to develop different ways of living. Mountains are the sources of rivers that provide water for many purposes, including the production ofelectricity. Many mountain ranges contain a variety of important minerals. Mountains also attract people for recreational uses. A large mountain system, like the Appalachian Mountains in northeastern Canada and the United States, may be called by different names in different areas. For example, the Appalachians in the southern United States are called the Blue Ridge, Great Smokies, Cumberland Plateau, and Black Mountains.