Fawn McKay grew up in a prominent and devout Mormon family in Huntsville, Utah. She earned a B.A. in English literature from the University of Utah and an M.A. from the University of Chicago. In 1936, she married scholar Bernard Brodie, the son of Jewish immigrants, who became a noted expert in Cold War military strategy. Both families opposed the marriage. Fawn Brodie worked for a while at the Harper Library at the University of Chicago, where she began doing the lengthy research for a biography of Mormon founder Joseph Smith, eventually published as No Man Knows My History (1944). The book received wide critical acclaim, but the Mormon Church strenuously objected to it and excommunicated Fawn Brodie as a heretic. She went on to write impressive works on Thaddeus Stevens, Sir Richard Burton, and Thomas Jefferson. The latter was a bestseller and the first to publicly prove that Jefferson had fathered children with the slave Sally Hemings. Fawn Brodie was also one of the first female professors of history at the University of California, Los Angeles.