Nebraska is roughly rectangular, except in the northeast and the east where the border is formed by the irregular course of the Missouri River and in the southwest where the state of Colorado cuts out a squared corner. The land rises more or less gradually from 840 ft (256 m) in the east to 5,300 ft (1,615 m) in the west. The great but shallow Platte River, formed in W Nebraska by the junction of the North Platte and the South Platte, flows across the state from west to east to join the Missouri S of Omaha. The Platte and the Missouri, together with their tributaries, give Nebraska all-important water sources that are essential to farming in this agrarian state. Underground water sources are also widely used for irrigation. The river valleys have long provided routes westward, and today the transcontinental railroads and highways follow the valleys.
From the Missouri westward over about half the state stretch undulating farm lands, where the fertile silt is underlaid by deep loess soil. Nebraska's population is concentrated there; many are farmers who produce grains for the consumer market or for feeding hogs and dairy cattle. In this region also lie Nebraska's two major cities—Lincoln, the capital and an important insurance center, and Omaha, the state's largest city and an important meat and grain distribution center—as well as many of the state's larger towns.
To the west and northwest the Sand Hills of Nebraska fan out, their wind-eroded contours now more or less stabilized by grass coverage. Cattle graze on the slopes and tablelands, protected in the severe winters by the sand bluffs and the valleys. The climate is severely continental throughout Nebraska; a low of - 40°F ( - 40°C) in the winter is not unusual, and during the short intense summers temperatures may easily reach 110°F (43°C). Rainfall is almost twice as heavy in the east as in the west. Yet in the west along the river valleys the mixture of silt and sand is watered enough to yield abundantly to cultivation, even under semiarid conditions. In the far west the land rises to the foothills of the Rocky Mts. and displays spectacular bedrock foundations.
Hundreds of fresh and alkali lakes in the state attract sportsmen and campers. The pioneers' migration west over the Oregon Trail is commemorated by the Scotts Bluff National Monument and the Chimney Rock National Historic Site. Other points of interest to the traveler include Father Flanagan's Boys Town, near Omaha; the Fort Niobrara National Wildlife Refuge, near Valentine; and the Homestead National Monument, near Beatrice.