The road to Big Mound began with the Dakota War of 1862, a six-week conflict in Minnesota that ended in the defeat of Little Crow and the dispersal of the Santee Sioux. Of 6,300 Santee, 2,000 were taken prisoner. Roughly 700 Lower Sioux from the Mdewakanton and Wahpekute bands remained at large, along with most of the 4,000 Upper Sioux from the Sisseton and Wahpeton bands, who had been reluctant participants. By the summer of 1863, more than 4,000 had gathered in a massive encampment of 600 lodges in Kidder County, joined by Teton, Yankton, and Yanktonai relatives. But Santee raids continued into 1863, killing more than a dozen settlers in Minnesota. General John Pope ordered Sibley to march west and punish the Santee. On June 16, Sibley departed from Fort Ridgely with 3,320 men -- infantry, cavalry, artillery, and scouts. It was the largest military expedition yet mounted against the Plains Indians.

Sibley's massive column crawled northwest across the Dakota prairie, slowed by drought, punishing heat, and a desperate shortage of drinkable water. For an entire month, the expedition did not encounter a single Indigenous person. Then a group of buffalo hunters, mostly Metis and Chippewa, told Sibley where to find the Santee encampment. He stripped his force to 2,056 combat-ready men -- 1,436 infantry, 520 cavalry, and 100 artillerymen with 60 mixed-blood and Sioux scouts -- and located the camp on July 24. Rather than attack immediately, Sibley tried diplomacy. He sent scout and interpreter Joseph LaFramboise, himself half Sioux, to propose a meeting with Standing Buffalo. Sibley believed, probably correctly, that Standing Buffalo and his followers wanted peace. But the camp also sheltered Inkpaduta, a Wahpekute leader whose hostility toward American expansion was absolute. Two opposing visions of the future occupied the same ground.

As the meeting took shape, Sioux and army scouts gathered peacefully on Big Mound, a hill 300 to 400 yards from Sibley's camp. Dr. Weiser's death transformed that gathering into a battlefield in seconds. Sibley estimated he faced 1,000 to 1,500 warriors, who took cover behind hills and in ravines. He sent two companies of Mounted Rangers forward to clear Big Mound, supporting them with additional soldiers and a six-pounder cannon. From the top of the mound, Sibley could see the full scope of what was unfolding: warriors forming a fighting retreat while the women and children of the camp fled westward, hauling what possessions they could carry. The Santee were badly outmatched in firepower. Only about half their warriors had guns, and ammunition was scarce. Several hundred Mounted Rangers pursued the retreating warriors until nightfall, pushing them roughly 12 miles west. Meanwhile, Sibley's infantry set about destroying the enormous quantities of jerky, buffalo robes, cooking utensils, and other supplies the Sioux had abandoned in their flight.

Sibley planned for his Rangers to camp where they stood and continue the chase at dawn. But a mistaken order recalled the cavalry to their base camp, 12 miles back the way they had come. The Rangers arrived exhausted, and Sibley was forced to rest both men and horses on July 25 before resuming the pursuit on July 26. That lost day gave the Sioux crucial time to regroup. Sibley's official report claimed 80 Indian casualties, but his private diary recorded only 9 killed. His own losses were three dead and four wounded. The discrepancy between the public report and the diary entry is a small window into the pressures of frontier military command, where generals answered to politicians who expected decisive results.

The tragedy of Big Mound is its contingency. Standing Buffalo appears to have been prepared to surrender his followers peacefully. One bullet from Tall Crown's weapon ended that possibility and triggered a cascade of violence -- the Battles of Dead Buffalo Lake and Stony Lake followed in quick succession as Sibley pursued the Sioux westward toward the Missouri River. Standing Buffalo and many of his followers eventually fled to Canada rather than continue fighting. Those who remained faced an army that would only grow stronger. Today the battlefield is open grassland, the mound itself a modest rise in the rolling prairie of central North Dakota. From the air, the terrain reveals why the engagement played out as it did: the hill provided a natural meeting point visible from both camps, while the ravines and folds of the surrounding prairie offered cover for warriors and escape routes for fleeing families. The landscape holds the shape of the story, even as the voices have gone silent.