The river level rises in March and April due to snowmelt in the lower elevations, and again in June as summer weather melts the higher-elevation snowpack.

The Powder River basin is shaped like a large shallow bowl, with its westernmost rock formations lying against the Big Horn Mountains.

For some 25 million years, the floor of this plain was made up of thick deposits of sandy silt from the surrounding mountains, with many rivers, deltas, backwaters and swamps, all covered by forests and vegetation.

Over long periods of time, the heavy plant growth died and accumulated as peaty layers in the large backwaters and swamps all across the basin.

These fires burned for a long time and they were extremely hot, and they baked and changed the structure of the sedimentary rocks that lay just over the coal seam until it became a hard "clinker" substance and turned a reddish brick color.

No Intestines led his band on a long migratory search for sacred tobacco, finally settling in southeastern Montana, where they became known as the Many Lodges or Mountain Crow.

[19] However, for two centuries, the Cheyenne and the many bands of Lakota people had been steadily migrating westward into the plains, and by 1851 they were established just to the south and east of Crow territory in Montana.

[20] Red Cloud's War (1866 to 1868) was a challenge by the Lakota to the military presence on the Bozeman Trail, which went to the Montana gold fields along the eastern edge of the Big Horn Mountains.

Red Cloud's War ended in a complete victory for the Lakota, and the 1868 Treaty of Ft. Laramie confirmed their control over all the high plains from the crest of the Big Horn Mountains eastward across the Powder River Basin to the Black Hills.

[21] Thereafter bands of Lakota led by Sitting Bull, Crazy Horse and others, along with their Northern Cheyenne allies, hunted and raided throughout the length and breadth of eastern Montana and northeastern Wyoming, including the area of the Tongue River Valley, until the Great Sioux War of 1876–1877.

Although early in the war on June 25, 1876 the Lakota and Cheyenne enjoyed a major victory over army forces under General George A. Custer at the Battle of the Little Big Horn, the Great Sioux War ended in the defeat of the Sioux and their Cheyenne allies, and their exodus from eastern Montana and Wyoming, either in flight to Canada or by forced removal to distant reservations.

After a running battle from Indian Territory to Montana, the battered remnants of this group arrived at Ft. Keogh, at the mouth of the Tongue, where a Northern Cheyenne band under Two Moons remained which had yet not been sent south.

By executive orders in 1884 and 1900, the federal government carved out a reservation for the Northern Cheyenne on Rosebud Creek, with the Tongue River as its eastern boundary.

The AFC was a rival of Tom Fitzpatrick's RMF Company and they had agents in the Crow villages including the notorious James Beckwourth, who was an adopted member of the tribe.

On August 29, 1865, General Conner, with a force variously estimated at about 300 soldiers, surprised an Arapahoe village of about 500 to 700 under Chiefs Old David and Black Bear camped on the Bozeman Trail, on the south side of the Tongue near present-day Ranchester, Wyoming.

[28][29] Two days after the battle with Conner, on August 31, 1865, warriors from the same Arapahoe village attacked a large wagon train of road-builders led by "Colonel" James A. Sawyers,[30] who were traveling on the Bozeman Trail, improving it as they went.

Lieutenant Colonel George A. Custer, with Companies A and B of the Seventh Cavalry, engaged and held off a larger Sioux force, including Hunkpapas, Oglalas, Miniconjous and Cheyennes at the Battle of Honsinger Bluff on August 4, 1873 about 7 miles (11 km) above the mouth of the Tongue on the Yellowstone River.

[35] Custer's command was part of the Stanley military column which was accompanying and protecting Northern Pacific Railroad survey parties in the summer months of 1873.

After remaining idle for more than two weeks on Goose Creek, on July 6, 1876 General George Crook ordered Second Lieutenant Frederick W. Sibley to take 25 men and two scouts, Big Bat Pourier and Frank Grouard, and make a reconnaissance to the north to locate the hostile Indian forces.

While traveling up the Tongue River in the vicinity of (present day) Dayton, Wyoming, the patrol discovered a large party of Sioux and Cheyenne warriors moving south and very close to them.

The war party followed closely, and after surviving attacks by pursuing Indians, the patrol abandoned their horses and traveled deep into the rough steep terraine of the Tongue River Canyon system on foot.

[41][42] On January 8, 1877 Colonel Miles and infantry units engaged in one of the last battles of the Great Sioux War of 1876-77 near Birney, Montana in the Tongue River Valley.

Limited farm lands that exist along flowing streams in the basin are usually irrigated from diversion dams, and produce crops which support the livestock industry—hay and feed stocks (corn, barley, alfalfa).

Dry land wheat farming, which is prevalent elsewhere in eastern Montana, occurs only in limited and scattered acreages in the Tongue River basin.

[citation needed] Historically, underground coal mines existed along the Tongue River at the communities of Monarch, Kleenburn and Acme, about 7 to 10 miles north of Sheridan, Wyoming.

Several large coal strip mines are presently operating in the area around the Tongue River Reservoir, near the small town of Decker, Montana about 20 to 23 miles northeast from Sheridan, Wyoming.

The current venture is the Tongue River Railroad, in various stages of planning for more than 30 years and intended to move coal from near Ashland to Colstrip.

The Tongue River Valley, before it reaches the Big Horn Mountains, is part of an extensive drainage basin which is an environment in which wild game thrives.

On the more southern tributaries, particularly in the Custer National Forest area, there are growing herds of prairie elk, an animal originally native to the plains of eastern Montana.

The Tongue River valley and surrounding area is the setting for "A Bride Goes West", an autobiography of Nannie Alderson, which relates her life as a ranch wife in the late 19th century in south central Montana.