The Elkhorn River enters the Platte west of Omaha, and the Loup River, formed by three tributaries flowing out of the Sand Hills, also discharges into the Platte.The Republican and Big Blue rivers flow through southern Nebraska, emptying into the Missouri in Kansas via the Kansas River.The Niobrara, a swift-moving stream that rises in the high country just west of the Wyoming border, flows across extreme northern Nebraska.The Ogallala Aquifer, a huge supply of underground water that made possible the extensive development of well irrigation, lies beneath most of Nebraska. The prairie soils of the southeast and the humus soils of central and northeastern Nebraska are important.
Nebraska lies within the Missouri River drainage system; the Platte, the major Nebraska tributary, joins the Missouri south of Omaha.
As one of the west-central states of the United States, Nebraska was primarily a stopover point for those migrating to the rich trapping country to the north and west as well as to the settlement and mining frontiers of the mountain and Pacific regions during the first half of the 19th century.
With the development of railroads after the American Civil War (1861–65) and the consequent immigration, the fertile soils of Nebraska were plowed, and its grasslands gave rise to a range cattle industry.
Nebraska is bounded by the state of South Dakota to the north, with the Missouri River making up about one-fourth of that boundary and the whole of Nebraska’s boundaries with the states of Iowa and Missouri to the east.
The boundary with Kansas to the south was established when the two territories were created by the Kansas-Nebraska Act in 1854.