An
island range is a mountain range that exists in total or almost total isolation from a larger chain of ranges and sub-ranges. From a distance on the plains, these ranges appear as "islands" of higher ground. They are often described as islands of mountainous land because they exist in the "sea" of lower elevation and flatter
prairie country, many examples are found in the northern
Rocky Mountains of the United States. Island ranges include the
Big Snowy Mountains of east-central
Montana and the
Crazy Mountains of south-central Montana. Island ranges, due to their isolation, often have animal and/or plant species or subspecies found nowhere else.