Winther was born into a Danish-American family as the youngest of six sons. The novelist
Sophus Keith Winther was one of his five brothers. After secondary education at
Eugene, Oregon's
Eugene High School, Oscar Winther matriculated at the
University of Oregon and graduated there in 1925 with a bachelor's degree in history. He became a graduate student in history and graduated in 1928 with an M.A. from
Harvard University and in 1934 with a Ph.D. from
Stanford University. His doctoral dissertation is titled
The Express and Stagecoach Business in California, 1848–60. After receiving his Ph.D., Winther held visiting positions at Stanford University and the San Jose Adult Education Center. He was elected a Fellow of the UK's
Royal Historical Society and a Fellow of the
Society of American Historians. In 1970 the Western History Association Council established the Oscar O. Winther award given each academic year in recognition of the peer-reviewed article judged to be the best published for that past year in the
Western Historical Quarterly. ==Articles==