As America’s 16th president, Abraham Lincoln left a towering legacy. His deep belief in the founding principles of American democracy—that every human deserved liberty and the opportunity for self-determination—compelled him to free enslaved African Americans. But when it came to the nation’s Indigenous peoples, who were collectively struggling for their lives, lands and cultural survival, he fell short of applying those cherished American ideals.

Lincoln, whose grandfather was killed by Indian raiders, had limited direct contact with Native Americans himself, despite having been raised on the frontier. As a young man, he volunteered to serve in the Black Hawk War, a conflict over tribal lands, but didn’t see combat.

During Lincoln’s presidency, tribal matters generally took a back seat to his all-consuming management of the Civil War and push to end slavery. While humanistically well intentioned, Lincoln was largely uninformed and reactionary on Native American issues and defaulted to policies set by his predecessors, writes University of Texas historian Thomas Britten. That meant making and breaking treaties, confiscating ancestral lands, forcing removal, pushing cultural assimilation—and, at times, turning a blind eye to acts of genocide committed by the military on the western frontier. Among the bitterest pills served to Native peoples during his administration: Lincoln signed laws that gave away millions of acres of tribal land to support white westward expansion, and he approved the hanging of 38 Dakota Sioux warriors, the largest mass execution in U.S. history.

“Lincoln’s acceptance of U.S. Indian policy indicated he conformed to the general social attitudes toward Native Americans in his time,” writes historian Christopher Anderson in the Journal of the Abraham Lincoln Association. “He continued to view them as a foreign people that would need to be removed through purchase or conquest.”

Lincoln grew up on the frontier in Kentucky and Indiana, where white settlers and Indigenous Americans frequently clashed over land. While the historical record reveals no significant contact with Native people in his youth, Abe grew up hearing fearsome stories from his father Thomas and uncle Mordecai about how their father, Abraham Sr., was killed by a small Indian war party in Kentucky while planting corn with his three sons.

In an autobiography Lincoln wrote for his 1860 presidential campaign, he described the killing as a “stealth” attack. He wrote to a relative, Jesse Lincoln, that the story “is the legend more strongly than all other imprinted on my mind and memory.”

At age 23, Lincoln enlisted as a volunteer in the Black Hawk War of 1832. Black Hawk, a revered warrior and leader, had long disputed the 1804 treaty that relinquished vast Sac and Fox Nation territories to the U.S. government in exchange for $1,000 in cash and goods each year. His effort to return to his ancestral home, which the government had sold to settlers, was deemed an “invasion of Illinois,” prompting the conflict.

Although Lincoln saw no combat during his three-month enlistment, he came away with a more mature and nuanced view of Native Americans. On one hand, he witnessed firsthand the fierceness of Indian warfare after he helped to bury fallen soldiers from his militia. But historical accounts also reveal that he developed a social rapport with Indian allies in camp. And one story recounts that he forcefully intervened to stop his fellow officers from shooting an elder Indian messenger, revealing his broader humanitarian impulses.

Under a policy intended to encourage volunteers and reward veterans, the government granted Lincoln a bounty-land warrant of 40 acres in Iowa and 120 acres in Illinois for his service.

During his time in the White House, Lincoln displayed the common paternalistic attitude that tribal peoples required white men's "civilizing" influence. The president, wrote biographer David Herbert Donald, “rather enjoyed playing the role of their Great Father, [sometimes] addressing them in pidgin English," as in one encounter with Potawatomi Indians in which he asked them, "Where live now? When go back Iowa?"—even though they spoke fluent English. In March 1863, when hosting Plains Indian dignitaries at the White House, Lincoln told them: “I can see no way in which your race is to become as numerous and prosperous as the white race except by living as they do, by cultivation of the earth.” He also argued, without a trace of irony, that despite being engaged in a bloody civil war, white men were “not, as a race, so much disposed to fight and kill one another as our red brethren.”

Presiding during a time when many white settlers were pushing West in search of farmable land and mineral wealth, Lincoln shared the prevailing U.S. government stance that tribal peoples posed obstacles to that expansion. In 1862 alone, he signed into law the Homestead Act and the Pacific Railroad Act, which shifted millions of acres of tribal land to settlers and railroad companies, respectively.

Distracted by the war, Lincoln left management of Indian affairs largely to corrupt local government agents and the military. And as frontier clashes accelerated, atrocities occurred. In 1864, the U.S. military forced an estimated 10,000 Navajo people on a march from their homelands to a desolate internment camp more than 300 miles away. The same year, a volunteer Colorado regiment brutally massacred more than 200 mostly unarmed Arapaho and Cheyenne men, women and children at Sand Creek, Colorado. And one week before the Emancipation Proclamation went into effect on January 1, 1863, Lincoln authorized the hanging of 38 Dakota Sioux men in the largest public execution in U.S. history.

The Dakota uprising that prompted the executions was borne of hunger and desperation. Ten years before the Civil War, the Dakota Sioux people had relinquished vast portions of the Minnesota Territory and been forced onto reservations in exchange for annual compensation in the form of gold and trade goods. But those promised government annuities often never arrived, as Indian agents intercepted the payments to cover alleged “debts” and the Dakota were starving. In 1858, the year Minnesota became a state, Sioux Chief Little Crow led a delegation to Washington to seek justice, but the U.S. instead reduced the reservation by half and opened it up to white settlers.

In 1861, Dakota farmers experienced crop failure, exacerbating their hunger. Anti-Indian sentiments at the time were exemplified by local trader Andrew Jackson Myrick, who refused the Dakota credit, allegedly responding to their starvation by saying, “So far as I am concerned, if they are hungry, let them eat grass.”

In August of 1862, four young Dakota men stealing eggs impulsively killed five white settlers near Acton Township. After the skirmish escalated to the murder of several hundred settlers, a volunteer militia under Henry H. Sibley responded to the conflict and a Dakota peace party of Native noncombatants initiated a peace process. But six weeks later, when the war ended, between 300 and 600 white settlers had been killed, along with more than 70 soldiers, as well as some 75 to 100 Dakota soldiers. One trader named Myrick was found dead, his mouth filled with grass.

While the Dakota War raged and settlers called for help, Lincoln was immersed in Civil War Union losses and grieving the loss of his 11-year-old son Willie, who had died earlier that year. The despondent, embattled president took more than a month to send military re-enforcements to end the conflict.

A military commission tried 392 Dakotas in six weeks for murder and other crimes. They sentenced 303 to hang for having “fired in battles, or brought ammunition, or acted as a commissary in supplying provisions to the combatants, or had committed some separate murder." On the last day alone, the commission decided nearly 40 cases.

Overall, historians say, the manner in which the trials were conducted was less than just. “The evidence was sparse, the tribunal was biased, the defendants were unrepresented in unfamiliar proceedings conducted in a foreign language, and authority for convening the tribunal was lacking,” said Carol Chomsky, associate professor at the University of Minnesota Law School and author of the paper “The United States-Dakota War Trials: A Study in Military Injustice.”

By law, Lincoln was responsible for approving the sentences. He faced a populace in Minnesota braying for blood revenge: On Nov. 26, 1862, the Goodhue Volunteer newspaper of Red Wing, Minnesota wrote, “Ten thousand men can be found who will dedicate their hopes, their fortunes, and if need be, their lives, to the extermination of the race.”

At first, Lincoln decided to only sentence to death those guilty of rape and dedicated himself to reviewing each case individually. He ultimately decided to also uphold the sentences of those guilty of “massacre” rather than battlefield killings. Lincoln described his intentions to the Senate, saying he was "anxious to not act with so much clemency as to encourage another outbreak on one hand, nor with so much severity as to be real cruelty on the other.”

Granting a reprieve to more than 260 of the condemned men, Lincoln signed off on executions for 39, of which one was given a last-minute reprieve. Known to this day as the “Dakota 38,” the condemned sang their death songs as they went to gallows on December 26, held hands on the platform and were executed before thousands of spectators.

They are remembered by their descendants among the Dakota, 3,000 of whom were expelled after the war from Minnesota under threat of death.