Bowman is believed to have been born Sarah Knight sometime between 1812 and 1813 (the 1860 census indicates her birth may have occurred as late as 1818) in either Tennessee or Clay County, Missouri. Raised on the American frontier, she received no formal education, and is believed to have been illiterate due to her use of an X on business and census forms. Despite the inability to read and write, she was bilingual by her later years, with a priest near Fort Yuma noting she was the first American woman he had met fluent in Spanish.