1822  Ashley-Henry Fur Traders on the Missouri River
1834  The Oglala Sioux become more centrally organized
1855  September 3, Colonel William Harney
uses 1300 soldiers to massacre an entire Brulé village in retribution for the killing of 30 soldiers who killed the Brulé chief over a cow.
1862  August 18, Beginning of the Sioux Uprising in Minnesota
1862  December 26, The mass execution of 38 mostly innocent Sioux men
for supposed crimes during the Sioux Uprising. The trials of almost every adult male were conducted under the premise of guilty until proven innocent.
1864  November 29, Massacre at Sand Creek
The Colorado Territory declares war on the Cheyenne. Colonel Chivington, a Methodist Minister turned military man, leads 700 soldiers to Sand Creek with the senseless purpose of killing peaceful Indians encamped there under US Government protection.

His band kill all 200 innocent men, women, and children. They parade through Denver with severed limbs, scalps, and body parts as battle souvenirs. Kitt Carson himself an Indian fighter denouced Chivington's actions as "that of a coward or a dog." The Cheyenne and Arapaho respond with wide spread massacre of settlers and soldiers across the frontier.

1865  July, General Patrick Conner organizes 3 columns of soldiers
to begin an invasion of the Powder River Basin. They had one order: "Attack and kill every male Indian over twelve years of age."
1865  July 24 - 26, Battle of Platte Bridge
The Cheyennes and Lakota besiege the most northerly outpost of the U.S. army and succeed in killing all members of a platoon of cavalrymen.
1865  End of August , Battle of Tongue River
Connor's column destroys an Arapaho village, including all the winter's food supply, tents and clothes. They kill over 50 of the Arapaho villagers.
1866  December 21,  Fetterman Massacre
Crazy Horse and Lakota warriors draw soldiers out of Fort Phil Kearney and ambush them. This was known as the Fetterman Massacre because the soldiers were led by Captain Fetterman, who boasted that he could defeat the entire Sioux Nation with a single company of cavalrymen.
1873  Custer and the Seventh Cavalry come to the northern plains
to guard the surveyers for the Northern Pacific Railroad. He has a chance encounter with Sitting Bull and Crazy Horse.
1876  The U.S. government issues an ultimatum that all Sioux
who are not on the Great Sioux Reservation by January 31 will be considered hostile. Most Sioux do not even hear of the ultimatum until after the deadline
1876  March 17, General George Crook's advance column attacks a Sioux/Cheyenne
camp on the Powder River. The people were driven from their lodges and many were killed.
1876  Spring, Sitting Bull organizes the greatest gathering of Indians on the northern plains.
The Battle of the Little Bighorn takes place where General George Armstrong Custer and 210 men under his command are killed.
1877  September 6,  Crazy Horse is killed at the hands of soldiers at Fort Robinson.
1883  Sitting Bull is allowed to go to the Standing Rock Reservation after surrender and two years prison.
1889  The Sioux sign an agreement with the U.S. government breaking up the great Sioux Reservation.