The last monolingual Chickasaw language speaker has died in her Oklahoma home at the age of 93.
Emily "Shonsh-She" Johnson Dickerson, spoke only Chickasaw for her entire life and was one of an estimated 70 remaining fluent speakers of the language.
Joshua Hinson, director of the Chickasaw Nation Language Department, said her death was "monumental".
He said: "I'm still trying to wrap my mind around the loss and what this means to the Chickasaw Nation."
Chickasaw Nation Governor Bill Anoatubby said: "Emily Dickerson was a treasured elder who held the Chickasaw language and ways of life close to her heart.
"This is a sad day for all Chickasaw people because we have lost a cherished member of our Chickasaw family and an unequalled source of knowledge about our language and culture.
"My condolences go out to her closest friends and family as we mourn the loss of a woman who holds a special place in the hearts of her family and her tribe."
Born on February 22, 1920, with the Chickasaw name of Shonsh-she, Emily Dickerson's childhood was spent in Oklahoma picking cotton, harvesting peanuts and chaffing broom corn as a farm labourer.
When she married in 1968, she raised her children to speak only Chickasaw until they enrolled in public school.
Her son, Carlin Thompson, said his mother's health had started to deteriorate after she fell and broke her hip a few months ago.
Her funeral took place on Saturday east of Ada near the Kullihoma ceremonial grounds on Chickasaw Nation land.
Native Indians from the Chickasaw tribe had their ancient homelands in Kentucky, Tennessee and the northern Mississippi and Alabama.
After encounters with European explorers and traders from England, France and Spain they were forced to sell their land in 1832 and move to the Indian Territory in Oklahoma during the era of Indian removal in the 1830s.
Their language, Chickashshanonmpa, was spoken by less than 1,000 speakers in 1994 and this figure has now dropped to less than 70, the majority of whom are over the age of 55.
Former astronaut John Herrington is one of the best-known members of the Chickasaw Nation.
He became the first enrolled member of a native American tribe to fly into space during a Space Shuttle mission in 2002.