The existence of the American grasslands is marked by irony. After many millennia of evolution, much of the grasslands were transformed to croplands within half a century by the European settlers. Grasslands have not vanished completely. There are nearly four million acres of National Grasslands, where one can still explore native prairie. The largest grassland formation is a huge area covered by tallgrass, mixedgrass, and shortgrass prairies that stretches from the Mississippi River to the Rocky Mountains called the Great Plains.
All grasslands have certain characteristics in common.
They generally exist on flat or rolling terrain, and the annual precipitation averages between ten and forty inches. However, quantity alone does not tell the whole story. The time of year when the precipitation falls is also important. Moreover, there are great fluctuations from year to year. At Buffalo Gap peak precipitation occurs during May through July and annual precipitation has varied from seven to twenty-six inches.