On January 23, 1870, 173 Blackfoot (140 women & children) were killed in Montana by the US Army. From the article:
"Soldiers massacre the wrong camp of Indians
Declaring he did not care whether or not it was the rebellious band of Indians he had been searching for, Colonel Eugene Baker orders his men to attack a sleeping camp of peaceful Blackfeet along the Marias River in northern Montana.
The previous fall, Malcolm Clarke, an influential Montana rancher, had accused a Blackfeet warrior named Owl Child of stealing some of his horses; he punished the proud brave with a brutal whipping. In retribution, Owl Child and several allies murdered Clarke and his son at their home near Helena, and then fled north to join a band of rebellious Blackfeet under the leadership of Mountain Chief. Outraged and frightened, Montanans demanded that Owl Child and his followers be punished, and the government responded by ordering the forces garrisoned under Major Eugene Baker at Fort Ellis (near modern-day Bozeman, Montana) to strike back.
Strengthening his cavalry units with two infantry groups from Fort Shaw near Great Falls, Baker led his troops out into sub-zero winter weather and headed north in search of Mountain Chief’s band. Soldiers later reported that Baker drank a great deal throughout the march. On January 22, Baker discovered an Indian village along the Marias River, and, postponing his attack until the following morning, spent the evening drinking heavily.
At daybreak on the morning of January 23, 1870, Baker ordered his men to surround the camp in preparation for attack. As the darkness faded, Baker’s scout, Joe Kipp, recognized that the painted designs on the buffalo-skin lodges were those of a peaceful band of Blackfeet led by Heavy Runner. Mountain Chief and Owl Child, Kipp quickly realized, must have gotten wind of the approaching soldiers and moved their winter camp elsewhere. Kipp rushed to tell Baker that they had the wrong Indians, but Baker reportedly replied, “That makes no difference, one band or another of them; they are all Piegans [Blackfeet] and we will attack them.” Baker then ordered a sergeant to shoot Kipp if he tried to warn the sleeping camp of Blackfeet and gave the command to attack.
Baker’s soldiers began blindly firing into the village, catching the peaceful Indians utterly unaware and defenseless. By the time the brutal attack was over, Baker and his men had, by the best estimate, murdered 37 men, 90 women, and 50 children. Knocking down lodges with frightened survivors inside, the soldiers set them on fire, burnt some of the Blackfeet alive, and then burned the band’s meager supplies of food for the winter. Baker initially captured about 140 women and children as prisoners to take back to Fort Ellis, but when he discovered many were ill with smallpox, he abandoned them to face the deadly winter without food or shelter.
When word of the Baker Massacre (now known as the Marias Massacre) reached the east, many Americans were outraged. One angry congressman denounced Baker, saying “civilization shudders at horrors like this.” Baker’s superiors, however, supported his actions, as did the people of Montana, with one journalist calling Baker’s critics “namby-pamby, sniffling old maid sentimentalists.” Neither Baker nor his men faced a court martial or any other disciplinary actions. However, the public outrage over the massacre did derail the growing movement to transfer control of Indian affairs from the Department of Interior to the War Department–President Ulysses S. Grant decreed that henceforth all Indian agents would be civilians rather than soldiers."