Rosario Cooper (1845–1917) was a yak titʸu titʸu yak tiłhini (Northern Chumash) woman who was the last known speaker of tiłhini (also known as Obispeño Chumash), though she had rarely spoken or heard it since her early childhood. During the last years of her life, Rosario worked with the linguist J.P. Harrington to recover what she could recall of her native language, and the pair were able to document some grammatical structure, place names, songs, and cultural knowledge before she died in 1917. Cooper is considered to be the last known speaker of Obispeño, though there has been some recent revitalization. Early life and family Cooper was born on October 5, 1845. Her father was Dr. Valentin "Frank" Cooper a medical doctor from England her mother was Ana Maria Higuera from the La Purisima Mission located in what is known today as Santa Barbara County. After her mother died in 1851, Cooper was raised by her older sister Agostina. At the time of her work with Harrington, Cooper was married to her third husband, Mauro Soto, and they lived together in the Lopez Canyon area in Arroyo Grande. Cooper had at least three children, only one of whom survived infancy. Cooper's son, Francisco Olivas, born to William Olivas and Rosario Cooper, was a father to several children and grandchildren, many of whom still reside in California and carry on Cooper's legacy. Cooper was baptized by a Franciscan priest in San Luis Obispo, and she practiced both Roman Catholic and Native beliefs. In addition, Cooper's work with Harrington revealed that she was interested in midwifery and had knowledge of native flora that could be used for healing purposes. Shortly before she died in 1917, Cooper helped to deliver one of her great-granddaughters. 1862 Homestead Act Rosario Cooper applied for, and received, 160 acres of land allocated under the Homestead Act of 1862 in San Luis Obispo County. The application (Homestead Certificate 6143, Application 11463) was perfected on November 28, 1896. The Homestead Act of 1862 was detrimental to many Native Americans and was instrumental in the continued genocide of the Indigenous Natives of the United States. Work with anthropologist J.P. Harrington From 1914 to 1916 for a total of around six or seven weeks, Cooper worked with the linguist J.P. Harrington to document what she could remember of her native language, Obispeño. Despite challenges facing Cooper and Harrington, such as Cooper's