Elena Zamora O'Shea, teacher, lay historian, and author, was born on July 21, 1880, at Rancho La Noria Cardenena near Peñitas, Hidalgo County, Texas, to Porfirio and Gavina (Moreno) Zamora. An aunt, Rita Zamora Villareal, raised her. Santiago Zamora and Concepción García de Moreno, descendants of a Spanish land-grant family, were her ancestors. In 1912 she married Daniel Patrick O'Shea of London, with whom she had two children. Elena grew up in the 1880s and 1890s on a rancho between the Nueces River and the Rio Grande. There she obtained an appreciation for rancho culture and education. Her family valued education, so all children on the rancho were taught to read and write (in Spanish). With public schools underdeveloped in Texas and especially in South Texas, Elena Zamora was sent to the Ursuline Convent, a boarding school, where she learned English. She furthered her education at the Holding Institute in Laredo, Southwest Texas Normal School in San Marcos, the University of Texas, the Normal School in Saltillo, Nuevo León, and the Universidad Autónoma de México in Mexico City. She attended Southwest Texas at the encouragement of José T. Canales.
In 1895 she took charge of the school at the family ranch in Palito Blanco, Jim Wells County, where she taught until 1902. Despite protests from her father (she wrote she had a motherless childhood), she began a teaching profession away from home at the King Ranch, where she was hired as a private tutor. In summer she taught school (the school year often consisted of three months) in the small settlements of Southwest Texas. Her first "city" job was in 1907–08 in Alice, where she served as a school principal and taught J. Frank Dobie. Her teaching career lasted twenty-three years. She apparently stopped teaching when she and Daniel moved in 1918 to Dallas, where she remained until her death.
From 1918 to 1923 Elena O'Shea worked as a translator for Sears-Roebuck and also taught Spanish. She conducted office and sales work for the family business, O'Shea Monument Works. She was a Democrat, a Catholic, and a member of the Dallas Woman's Forum and the Latin American League. She lamented the lack of a historical account of her forefathers, Spanish land-grant settlers who had fought for Texas independence. In 1935, on the eve of the Texas Centennial, she wrote El Mesquite, a fictionalized history of Mexican settlers between the Nueces River and the Rio Grande from 1575 to the early 1900s. Using the autobiographical voice of an old mesquite tree, she began "I am of the highest quality of Mesquites" and proceeded to describe eyewitness accounts of life and events among the settlers. In eleven chapters the book describes plant and animal life, the settlers of El Ranchito (the area that is now Corpus Christi), customs and manners, weddings, life in Nuevo Santander, other settlements in South Texas before the Anglo-Americans arrived, the rise of a vaquero culture, the Civil War, changing land and transportation patterns, and women's work, material culture, and folklore. She also mentions relations with the Irish, Germans, and several Indian tribes.
El Mesquite, like Emilia Schunior Ramírez Ranch Life in Hidalgo County after 1850 and the work of Jovita González de Mireles, both from South Texas, helped preserve the Texas-Mexican story. According to an obituary, Elena O'Shea "helped many other historians set the record straight." She was one of three Mexican-descent women in the 1937 Texian Who's Who, and her obituary appeared in the Cattleman. She died on March 23, 1951, in a Dallas hospital and is buried at Calvary Hill Cemetery there.