Eastern Wyoming and western Nebraska is a semiarid region situated in temperate latitudes. The North Platte and Platte Rivers which combine to form the major through-flowing drainage can be characterized as low gradient bedload streams with sandy bottoms. The bed material of Sybille Creek, the Laramie River, and the North Platte and Platte Rivers consists of texturally submature, subquartzose sands with nearly equal amounts of feldspar and rock fragments. Within the Platte system, feldspar and granitoid rock fragments undergo more than 600 km of transport without showing a significant reduction in amount or change in relative grain size. The effect of abrasion during transport on the composition of Platte River sands is minimal.