The American prairie was occupying most of the central part of the United States until the 1800's and it was stretching on the territories of the states of Texas, New Mexico, Oklahoma, Kansas, Colorado, Nebraska, Wyoming, Montana, South Dakota, and North Dakota. The American prairie was a vast grassland but that changed significantly after the 1800's and most of prairie is now gone at the expense of converting it to agricultural land, the biggest and most important agricultural land in the United States.