Oscar Haas, historian of New Braunfels and Comal County, was born on October 12, 1885, the eldest child of Ernst Georg and Ottilie (Rochau) Haas. Both the Haas and Rochau families were German New Braunfels settlers who moved to the Crane's Mill area "in the mountains" of Comal County soon after the Civil War. The farm at Crane's Mill where Haas was born, six miles west of New Braunfels, is now at the bottom of Canyon Lake. Haas spent his early life on his family's farm on the Little Blanco River in Blanco County and attended a nearby public school. In 1897 the family moved to New Braunfels, and Oscar began third grade at New Braunfels Academy. After he finished the sixth grade, he began working for druggist-merchant August Forke. He also began exploring Comal County on his bicycle, riding along country roads and taking pictures or making pencil sketches of animals, houses, and people.
He married Clara Amelia Conring in June 1918, and in time she became his partner in German translation and annotation. As a young man Haas was employed by the large mercantile firm of Pfeuffer and Holm as men's-wear salesman. For a brief time he became a partner in a retail clothing, dry-goods, and shoe store. He was elected county treasurer in 1934 and served in that office for twenty-eight years. By 1940 he had begun to discover, collect, and translate material on old New Braunfels and Comal County and its citizens. While working in the courthouse he saved the earliest records of the county from destruction and had them recorded in the Texas State Archives and preserved for future historic reference. After that he began writing for publication. The Neu Braunfelser Zeitung and the New Braunfels Herald published the series "Know Comal County," taken from commissioners' court records dating from August 12, 1846, which ran for three years. Continuing in the same vein, Haas wrote another series for both papers in 1944–45, "99 Years Ago" and "100 Years Ago," tracing the history of the German settlement of New Braunfels. He published a number of other articles in the two newspapers, and after 1957 his first-time translations of Hermann Seele's "Die Cypresse," Fritz Goldbeck's history poems on the settling of New Braunfels in the mid-1840s, and portions of the largely untranslated papers of Prince Carl of Solms-Braunfels appeared in the New Braunfels Herald-Zeitung.
Beginning in 1961 Haas and his wife produced a landmark history series in 144 weekly installments, "Comal County in the Civil War," translated from Ferdinand Lindheimer's German-language newspaper of the 1860s, the Neu Braunfelser Zeitung. In 1962 Haas retired from his job as country treasurer in order to devote time to the compilation of his large collection of historic materials and to produce his definitive History of New Braunfels and Comal County, Texas, 1844–1946 (1968). His other major publications include Chronological History of the Singers of German Songs in Texas (1948), The First Protestant Church, Its History and Its People: 1845–1955 (1955), and a translation of the Civil War diary of Capt. Julius Giesecke of New Braunfels.
Haas's expertise qualified him as a historian and archivist-collector of photographs, pamphlets, books, broadsides, maps, family letters, and diaries. He preserved early records and histories and, with Clara, was an authority on old Comal County structures. He supplied the names of New Braunfels founders for the stone Fachwerk memorial in their honor in Landa Park. His awards were numerous; among them were an award for historical writing from the Historical Society of the Evangelical and Reformed Church, Lancaster, Pennsylvania, in 1959; the San Antonio Conservation Society History Award in 1963; and the Besserung Award for Outstanding Community Service from the Comal County Chamber of Commerce in 1964. He was also a member of several German singing societies and a collector of Indian artifacts. Haas died in Boerne, Texas, on February 20, 1981, and was buried in New Braunfels City Cemetery; he was survived by his wife and three children.