Eastern Colorado

The Eastern Plains of Colorado refers to a region of the U.S. state of Colorado east of the Rocky Mountains and east of the population centers of the Front Range.

The Eastern Plains are part of the High Plains, which are the westernmost portion of the Great Plains. The region is characterized by mostly rolling plains, divided by the South Platte River and Arkansas River valleys. There are also several deciduous forests, canyons, buttes, and a few large natural lakes and rivers throughout the region. The Eastern Plains rise from approximately 3,400 feet (1,000 m.) at the eastern border of Colorado with Kansas, where the Arkansas River leaves the state, to 7,500 feet (2,300 m.)^{[citation needed]} east of the Denver Basin.

Most of the Eastern Plains region lies within Colorado's 4th congressional district.

The Eastern Plains have a semi-arid climate and receive little rainfall. Much of the area relies on irrigation to survive. Summers are typically hot and dry, often bringing thunderstorms, which are often severe, to the area, with some occasionally forming landspouts and tornadoes. Eastern Colorado winters are cold and dry, with significant snowfalls and icy conditions. Temperatures can sometimes fall to -40 to -30 degrees Fahrenheit in extreme cold waves, although this is rare.

Eastern Colorado was once home to many Native American tribes. The Plains Indians that lived in the region included the Arapahoe, Cheyenne, Kiowa, Pawnee, and Sioux. The Ute people formally ruled all over central and western Colorado, and onto the eastern plains as well. The Comanche once ruled all over southeastern Colorado, and the Jicarilla Apache ruled in southeastern Colorado as well.

In 1541, the Spanish came to the area now known as the south eastern portion of Colorado, in search of gold after hearing rumors in Mexico city. Not having found any gold, the Spanish largely left the area untouched. During the late 17th and 18th century Spain and France claimed southeastern Colorado. However, nobody settled the land. In 1803 the United States gained possession of much of the land east of Rocky Mountains with the Louisiana Purchase.

Zebulon M. Pike was sent by the federal government to lay out the boundary lines of territory in 1806. This expedition investigated the area now known as Colorado Springs. The prominent mountain in the area was named Pike's Peak after Pike, the leading commander of the exploration. There were multiple expeditions sent to lay out and explore the territory throughout the early 1800s. This created multiple trading posts with fur trades attracting many backcountry adventurers. There was still no permanent settlement created until after the conclusion of the Mexican War in 1848. San Luis was founded on the Culebra River in 1851. Spanish-speaking settlers who had moved north from New Mexico founded it. San Luis was shortly followed by settlements of San Pedro, San Acacio and Guadalupe.

The Eastern Colorado plains are among the most sparsely populated areas in the continental United States. Some of the region, with the exception of comparatively urban areas like Sterling, is experiencing depopulation, which in some areas began with the influenza pandemic of 1918 and agricultural price collapses after World War I. The Dust Bowl devastated the region and further accelerated this outmigration, with people migrating to Denver. Baca County is emblematic of the population decline and its associated effects, as the county's population declined in every census from 1960 to 2020.