In southwestern Minnesota, explorers and later settlers encountered a vast tallgrass prairie that looked like waves upon the sea when the wind blew. Home for centuries to American Indians, this grassland was unlike the forested eastern United States and stretched as part of a broad prairie from Illinois to the Rocky Mountains, with grass up to six feet high and scattered trees near lakes and streams. Prairie, a French word for meadow, is an expanse duplicated in few other parts of the world, including the pampas of Argentina and the Black Earth Belt of Russia. Of the three types of prairie—short grass, mix grass, and tall grass—it was the tall grass prairie that covered southwestern Minnesota, dominated by Big Bluestem, Indian Grass, and Switch Grass. Pollen records indicate that prairies were established after the retreat of the Wisconsin Glacier some 18,000 years ago, and their pattern was maintained over time by moisture or lack of it, fires, and the difficulty other seedlings had competing once prairie sod was established. Today only small patches remain in reserves or untillable areas, and most of the trees now seen were planted as shelter belts by homesteaders and later farmers. Though the prairie disappeared after nourishing buffalo for years, it continues to nourish through the rich corn belt farmlands created by thousands of years of rotted grass roots.