f which followed the Yellowstone for a short length.
Native American anger at settler intrusion into the hunting grounds led to Red Cloud's War. The conflict was settled with the Treaty of Fort Laramie in 1868, by which the US granted the territory of the Black Hills and the Powder River Country to the Lakota people.  This region included the drainages of the Big Horn, Powder and Tongue rivers. The discovery of gold in 1874 in the Black Hills, however, attracted thousands of miners who invaded the sacred grounds, and conflicts broke out with the Sioux.
The new competition and violence led to the Great Sioux War of 1876-77. The US sent in troops to protect the miners, although they had violated the treaty, and to defeat the Sioux. In 1876, Colonel John Gibbon led a column of men from Fort Ellis near Bozeman, Montana and traveled down the Yellowstone to meet up with General Alfred Terry's Dakota Column, which had traveled upstream from North Dakota. Terry formed a base of operations at the mouth of Rosebud Creek on the Yellowstone, but the US miscalculated the strength of the Lakota who had gathered by the thousands along the river. Lieutenant Colonel George Armstrong Custer departed from Rosebud Creek with the 7th Cavalry on the expedition that ended in his complete defeat by the Lakota and Cheyenne at the Battle of the Little Bighorn. The army ferried its survivors down the Yellowstone to Fort Abraham Lincoln on the Missouri River.
After the US achieved victory the tribes were forced onto reservations. The Sioux and allies were forced from eastern Montana and Wyoming: some bands fled to Canada, while others suffered forced removal to distant reservations, primarily in present-day South Dakota and Nebraska west of the Missouri River. Crow warriors had enlisted as scouts with the US Army during the war and the Crow Indian Reservation was established in south-central Montana. The Northern Cheyenne Indian Reservation is south of the Yellowstone in Montana.
Many of the early expeditions to the area that would later become Yellowstone National Park traveled along the Yellowstone River, including the Cook–Folsom–Peterson Expedition and the Washburn-Langford-Doane Expedition. In the early 1870s, the Northern Pacific Railroad attempted to extend rail service along the Yellowstone to Livingston from Bismarck, North Dakota, a route proposed to cross the last of the Lakota buffalo hunting grounds.  This route was finally completed in 1883. By the early 20th century, Northern Pacific was providing train service along the river to the north entrance of the park near Gardiner.
Flooding occurs in the watershed due to snowmelt, rainfall, and intense thunderstorms. In higher elevations, snowmelt can cause flood conditions due to rapid snowmelt in spring and early summer. In lower elevations, regional rainstorms and intense thunderstorms can cause flooding in summer and fall.  Severe droughts have occurred in the Yellowstone Watershed lasting several years. Droughts have occurred in the basin in 1929-42, 1948–62 and 1976-82. The 1977 drought affected most the western United States and lead to decreased streamflows in the watershed. The reduced flow increased dissolved solids concentrations in the basin. Water quality varies across the various rivers in the basin. In mountainous areas, suspended sediment and dissolved solid concentrations are lower than in basin and plain areas. Human activities, including agriculture and mining, along with natural sources contribute to suspended sedimentation levels in plain areas. In addition, fecal bacteria, salt, and selenium contamination is present in some streams within the watershed. 
An ExxonMobil pipeline which runs from Silver Tip, to Billings, Montana, ruptured about 10 miles (16 km) west of Billings on Friday, July 1, 2011, at about 10:40 p.m.  The resulting spill leaked an estimated 1,500 barrels of oil, equivalent to 63,000 US gallons (240,000 l; 52,000 imp gal), into the Yellowstone River for 56 minutes before it was shut down.  As a precaution against a possible explosion, officials in Laur