Mary Sophie Young, botanist, was born in Glendale, Ohio, on September 20, 1872 (possibly 1870), the daughter of Charles Huntington and Emma Adams (Sainer, Saver, Sawer) Young. She attended Ohio public schools, Harcourt Place Seminary, and Wellesley College, from which she received a B.A. degree in 1895. From that time until 1906 she taught in schools in Missouri, Illinois, Kansas, and Wisconsin and took correspondence courses from the University of Chicago. She attended the University of Chicago from 1906 to 1910, when she received a Ph.D. degree from that institution. In the fall of 1910 Young joined the University of Texas faculty as a botany tutor. She was promoted to the rank of instructor the following year. In 1912 she was assigned to teach a course in taxonomy and put in charge of the university's herbarium. She found Austin an excellent area for collecting specimens because of its location on a line where the eastern and western flora meet. Despite numerous difficulties encountered in her frequent field trips, she enriched the holdings of the herbarium through the collection of new Texas specimens and the exchange of duplicates with other states. In 1917 Young's A Key to the Families and Genera of the Wild Plants of Austin, Texas was published as University of Texas Bulletin No. 1754; this work and another, The Seed Plants, Ferns and Fern Allies of the Austin Region, published in 1920 as University of Texas Bulletin No. 2065, reflected her pioneer work in the field of plant classification in the Austin area. Young also collected specimens in other areas in central Texas, but her favorite subject was the flora of West Texas. With the exception of the summer of 1917 (which she spent in the Panhandle), she spent the summers of 1914 through 1918 in the Trans-Pecos area of Texas. From large areas of rugged and mountainous country she brought back hundreds of plants previously unrepresented in the university's herbarium. She became ill early in 1919 and died of cancer on March 5, 1919. Young was buried in Oakwood Cemetery in Austin. Her journal for the summer 1914 expedition to the Trans-Pecos area was published posthumously in two issues of the Southwestern Historical Quarterly (January, April 1962).