The Battle of Killdeer Mountain (also known as the Battle of Tahkahokuty Mountain) took place during Brig. Gen. Alfred Sully's expedition against the Sioux in Dakota Territory July 28–29, 1864. The location of the battleground is in modern Dunn County, North Dakota. With a total of more than 4,000 soldiers involved in the total operation, and more than 2,000 in the battle, Sully's expedition was the largest ever carried out by the U.S. army against Native Americans.
Background
In the aftermath of the Dakota War of 1862, the U.S. government punished the Sioux, including those who had not participated in the war. Large military expeditions into Dakota Territory in 1863 pushed most of the Sioux to the western side of the Missouri River at least temporarily and made safer, although not entirely safe, the frontier of white settlement in Minnesota and the Dakotas. Four whites were killed by Sioux raiders in the spring of 1864.
An important impetus to another military campaign against the Sioux was the desire to protect lines of communication with recently discovered goldfields in Montana and Idaho. The lifeline for the American gold miners were steamboats plying the Missouri River through the heart of Sioux territory. During the winter of 1863–1864, Sully's superior, Major General John Pope ordered Sully to establish several forts along the Missouri River and in the eastern Dakotas to secure the communication routes to the goldfields and to eliminate the Sioux threat to the settlers east of the Missouri River.
Sully's First Brigade, consisting of up to 1,700 men, followed the Missouri River from its starting point at Sioux City, Iowa. The Second Brigade with about 1,550 men would march overland from Fort Ridgely in Minnesota. On the march up the Missouri, the Sioux killed one soldier and wounded another. The three Sioux perpetrators were caught, killed, and decapitated. Additional soldiers and civilians with 15 steamboats chugged up the Missouri River to support the army on the ground.
Sully's two columns of soldiers united on June 29 and on July 7 he established Fort Rice on the Missouri River in North Dakota as a base, supplied by steamboat, for his military expedition. His scouts, Winnebago and friendly Sioux and mixed-bloods, informed him of a large encampment of Sioux 130 miles northwest near the Little Missouri River. On July 19, he and his men departed Fort Rice to search for the Sioux encampment. Sully was encumbered by a wagon train of 200 miners and their families headed for the goldfields who he reluctantly agreed to protect and escort.
Sully's scouts reported 1,500 to 1,800 tipis in the Sioux encampment. Sully believed he would be faced by 5,000 to 6,000 warriors. The Sioux later claimed they had 1,600 warriors in the battle – likely closer to the truth with a calculation of one to two adult males per tipi. The Sioux in the encampment consisted mostly of Lakota (Teton) from the Hunkpapa, Sihasapa, Miniconjou, and Sans Arc bands plus Yanktonais, and a few Santees. The Sioux were mostly armed only with bows and arrows and a few short-range muskets and shotguns. Many of the Sioux, especially the Tetons, had not been hostile to the U.S. before this encounter.
Sully, after leaving men at Fort Rice and to guard the emigrants, had 2,200 men for the attack. He also had two artillery batteries with eight howitzers. On July 26, Sully's Indian Scouts skirmished with 30 Sioux warriors near present-day Richardton, North Dakota and one scout was wounded. With the Sioux now aware of his presence, Sully advanced rapidly but carefully. On the morning of July 28, scout Frank LaFramboise, a mixed blood Santee, informed Sully of the location of the large Sioux encampment 10 miles ahead.
Killdeer Mountain was at the edge of the Dakota badlands, cut up by "deep, impassable ravines" and "high rugged hills." Realizing that a cavalry charge would be difficult in the broken terrain Sully dismounted his soldiers and formed them in a hollow square, one mile and a quarter (2 km.) per side. His horses and artillery were sheltered inside the square. He advanced on foot, as the Sioux on horseback formed up in groups on Sully's flanks and on hilltops.
Battle
The two sides, Sully' soldiers drawn up in a hollow square and Native forces scattered around the hills, exchanged insults at long distance. One warrior, a Hunkpapa named Lone Dog rode within rifle range of the soldiers, taunting them. Sully ordered him shot by sharpshooters. Accounts differ as to whether Lone Dog was killed or unscathed.