Following the U.S. Civil War, regiments of African American men known as buffalo soldiers served on the western frontier, battling Native Americans and protecting settlers. The buffalo soldiers included two regiments of all-Black cavalry, the 9th and 10th cavalries, formed after Congress passed legislation in 1866 that allowed African Americans to enlist in the country’s regular peacetime military.

The legislation also brought about the creation of four Black infantry regiments, eventually consolidated into the 24th and 25th infantries, which often fought alongside the 9th and 10th cavalries. Many of the men in these regiments, commanded primarily by white officers, were among the approximately 180,000 African Americans who served in the Union Army during the Civil War.

For more than two decades in the late 19th century, the 9th and 10th cavalries engaged in military campaigns against hostile Native Americans on the Plains and across the Southwest. These buffalo soldiers also captured horse and cattle thieves, built roads and protected the U.S. mail, stagecoaches and wagon trains, all while contending with challenging terrain, inadequate supplies and discrimination.

It’s unclear exactly how the buffalo soldiers got their nickname. Archivist Walter Hill of the National Archives has reported that, according to a member of the 10th Cavalry, in 1871 the Comanche bestowed the name of an animal they revered, the buffalo, on the men of the 10th Cavalry because they were impressed with their toughness in battle. (The moniker later came to be used for the 9th Cavalry as well.)

Other sources theorize the name originated with the belief of some Native Americans that the soldiers’ dark, curly, black hair resembled that of a buffalo. Others say it is because the soldiers covered up with buffalo hides during winter to try to keep warm. Whatever the case, the soldiers viewed the nickname as one of respect, and the 10th Cavalry even used a figure of a buffalo in its coat of arms.

When the American-Indian Wars ended in the 1890s, the buffalo soldiers went on to fight in Cuba in the 1898 Spanish-American War; participate in General John J. Pershing’s 1916-1917 hunt for Mexican revolutionary Pancho Villa, and even act as rangers in Yosemite and Sequoia national parks.

In 1948, President Harry Truman issued an executive order eliminating racial segregation and discrimination in America’s armed forces; the last all-Black units were disbanded during the first half of the 1950s. The nation’s oldest living buffalo soldier, Mark Matthews, died at age 111 in Washington, D.C., in 2005.