Cordelia (Cordia) Duke, rancher, writer, and game warden, was born near Belton, Missouri, on January 10, 1877, the daughter of A. R. C. and Belle (Wingert) Sloan. She attended school in Overbrook, Kansas, where her family moved shortly after her birth. She passed the teachers' examination at the age of sixteen and taught school for several years in the Cherokee Nation, Oklahoma Territory, before moving to Sherman County, Texas. In September 1906 she began teaching in a four-pupil school on a strip of Texas land between Oklahoma and the XIT Ranch. There she met Robert L. Duke, then foreman of the Buffalo Springs division of the XIT. The story goes that after returning with her charges from a late roundup near El Frio Springs, Cordia was warned by one young cowboy not to "fool with that Bob Duke," who had fired a cowhand for mistreating a horse. She took her chances anyway, and she and Duke were married on January 9, 1907; they eventually had three daughters. Duke became general manager of the XIT under Henry S. Boice, and when the ranch ceased its cattle operations in 1912, he was retained to oversee that portion of the range leased to the Shelton and Trigg partnership.
During her years as a ranch wife, Cordia Duke kept a diary in which she noted details of a rapidly vanishing way of life. She used these and reminiscences of the ranchhands in articles for such newspapers and magazines as the Cattleman. Later, excerpts from this diary were used as the basis for a book entitled 6,000 Miles of Fence, which she coauthored with Joe B. Frantz. This book, published in 1961, was the first in the M. K. Brown Range Life Series of the University of Texas Press. In the 1920s, when the land around the Duke homestead was designated a wildlife sanctuary, Mrs. Duke was appointed game warden, the first woman to hold that job in Texas. She was warden for a number of years and became legendary for her rapport with the thousands of wild ducks that found refuge on the sanctuary during their annual migrations. After her husband's death in 1933, Cordia Duke moved to Dalhart, where she died on July 23, 1966, and was buried.