The Powder River Country refers to an area of the Great Plains

Great Plains

The Great Plains are a broad expanse of flat land, much of it covered in prairie, steppe and grassland, which lies west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...

 in northeastern Wyoming

Wyoming

Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. The area is loosely defined between the Bighorn Mountains and the Black Hills

Black Hills

The Black Hills are a small, isolated mountain range rising from the Great Plains of North America in western South Dakota and extending into Wyoming, USA. Set off from the main body of the Rocky Mountains, the region is something of a geological anomaly—accurately described as an "island of...

, in the upper drainage areas of the Powder

Powder River (Montana)

Powder River is a tributary of the Yellowstone River, approximately long in the southeastern Montana and northeastern Wyoming in the United States. It drains an area historically known as the Powder River Country on the high plains east of the Bighorn Mountains.It rises in three forks in eastern...

, Tongue

Tongue River (Montana)

The Tongue River is a tributary of the Yellowstone River, approximately 265 mi long, in the U.S. states of Wyoming and Montana. The Tongue rises in Wyoming in the Big Horn Mountains, flows through northern Wyoming and southeastern Montana and empties into the Yellowstone River at Miles City,...

, and Little Bighorn

Little Bighorn River

The Little Bighorn River is a tributary of the Bighorn River in the United States in the states of Wyoming and Montana. The Battle of the Little Bighorn was fought on its banks in 1876, as well as the Battle of Crow Agency in 1887....

 rivers.

During the late 1860s, the area was the scene of Red Cloud's War

Red Cloud's War

Red Cloud's War was an armed conflict between the Lakota, Northern Cheyenne, and Arapaho and the United States in the Wyoming Territory and the Montana Territory from 1866 to 1868. The war was fought over control of the Powder River Country in north central present day Wyoming...

 between the Lakota and the United States. The Lakota victory in the war resulted in the preservation of their control of the area for the next decade.

After control fell to the U.S. government in 1870s following the end of the Great Sioux War of 1876-77

Great Sioux War of 1876-77

The Great Sioux War of 1876, also known as the Black Hills War, was a series of battles and negotiations which occurred between 1876 and 1877 involving the Lakota and Northern Cheyenne, against the United States...

, the area was opened to white settlement, one of the last such areas opened for homesteading

Homesteading

Broadly defined, homesteading is a lifestyle of simple self-sufficiency.-Current practice:The term may apply to anyone who follows the back-to-the-land movement by adopting a sustainable, self-sufficient lifestyle. While land is no longer freely available in most areas of the world, homesteading...

 in the continental United States. In 1892, the area was the scene of the Johnson County War

Johnson County War

The Johnson County War, also known as the War on Powder River, was a range war which took place in April 1892 in Johnson County, Natrona County and Converse County in the U.S. state of Wyoming...

 between land barons and Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

an immigrants. The conflict was depicted in the 1981 movie Heaven's Gate.

In the early 20th century, the discovery of petroleum

Petroleum

Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

in the area led to the development of the area's oil fields.