From the “Trail of Tears” to Wounded Knee and Little Bighorn, the narrative of American history is incomplete without the inclusion of the Native Americans that lived on the continent before European settlers arrived in the 16th and 17th centuries. Since the first contact between natives and settlers, tribes like the Sioux, Cherokee, and Navajo have both fascinated and perplexed outsiders with their history, language, and culture.

The history of the Sioux is replete with constant reminders of the consequences of both their accommodation of and resistance to American incursions into their territory by pioneering white settlers pushing further westward during the 19th century. Some Sioux leaders and their bands resisted incoming whites, while others tried to accommodate them, but the choice often had little impact on the ultimate outcome. Crazy Horse, who was never defeated in battle by U.S. troops, surrendered to them in 1877, only to be bayoneted to death by soldiers attempting to imprison him. Black Kettle, who flew a large American flag from his lodge to indicate his friendship with the white man, was shot to death by soldiers under George Custer’s command in 1868.

Throughout the 19th century, the U.S. government and its officials in the West adopted a policy of dividing the Sioux into two groups: “Treaty Indians” and “Non-treaty Indians.” Often they used these groups against each other or used one group to influence another, but the end was always the same. They were forced off the land where they resided, their populations were decimated by disease, and they were forced onto reservations to adopt lifestyles considered “appropriate” by American standards.

Despite being one of the most erstwhile foes the U.S. government faced during the Indian Wars, the Sioux and their most famous leaders were grudgingly admired and eventually immortalized by the very people they fought. Sitting Bull and Crazy Horse remain household names due to their leadership of the Sioux at the fateful Battle of the Little Bighorn, where the native warriors wiped out much of George Custer’s 7th Cavalry and inflicted the worst defeat of the Indian Wars upon the U.S. Army. Red Cloud remains a symbol of both defiance and conciliation, resisting the Americans during Red Cloud’s War but also transitioning into a more peaceful life for decades on reservation.

However, one of the more overlooked conflicts the U.S. Army had with the Sioux took place during the American Civil War. It is known by various names, including the Dakota War, the US-Dakota War, the Dakota Uprising, the Sioux Outbreak, and Little Crow’s War (after the principal Dakota leader), but the current most commonly used name for the war is the “Dakota War.” Two of the four Dakota tribes in the state unleashed their anger and frustration on largely immigrant communities that were heavily German or Norwegian, and the massacres took a heavy toll. In the process, the conflict featured the largest Indian siege of an Army fort in American history, and the end of the conflict brought the largest mass execution in American history.

Indeed, the total loss of life during the Dakota War was perhaps the second largest of all the Indian Wars in North America, second only to the bloody King Philip’s War in colonial New England in the late 17th century, during which more than 1,000 settlers were killed. Throughout the Dakota War, as many as 800 whites were killed, although no one knows the total, and many of the victims were buried in anonymous mass graves. The Dakota losses are unknown but sizable, and after both wars, the natives involved suffered catastrophic ramifications.