The most quoted statement dealing with Eliza R. Snow’s relationship with Joseph Smith was made by Angus Cannon when recounting his conversation with Joseph Smith III:
He [Joseph Smith III] said, “I am informed that Eliza Snow was a virgin at the time of her death.” I in turn said, “Brother Heber C. Kimball, I am informed, asked her the question if she was not a virgin although married to Joseph Smith and afterwards to Brigham Young, when she replied in a private gathering, ‘I thought you knew Joseph Smith better than that.’”1
Less commonly referenced is an 1877 letter from Eliza to Daniel Munns, an RLDS member:
You ask (referring to Pres. Smith), “Did he authorize or practice spiritual wifery? Were you a spiritual wife?’I certainly shall not acknowledge myself of having been a carnal one” . . . . I am personally and intimately acquainted with several ladies now living in Utah who accepted the pure and sacred doctrine of plural marriage, and were the bona fide wives of Pres. Joseph Smith.” (Emphasis in original.)2
This firsthand statement seems to indicate either that Eliza did not have sexual relations with the Prophet or she was carefully trying to avoid admitting to it, even though she freely implied its occurrence with Joseph’s other plural wives.
Evidence presented in 2016 by BYU-Idaho professor Andrea Radke Moss supports that Eliza may have been raped in Missouri and perhaps thereafter was not sexual active. If true, this would help explain Eliza’s comments to Munns quoted above. See “Eliza R. Snow as a Victim of Sexual Violence in the 1838 Missouri War– the Author’s Reflections on a Source.”
Stories and rumors have sprung up regarding Eliza’s relationship with Joseph and Emma Smith suggesting that Eliza became pregnant and Emma threw her down a stair causing her to lose the baby and become infertile thereafter. Such folklore is examined in Brian C. Hales, “Emma Smith, Eliza R. Snow, and the Reported Incident on the Stairs,” Mormon Historical Studies, vol. 10, no. 2, Fall 2009, 63–75.
For more details, see Brian C. Hales (with Don Bradley), Joseph Smith’s Polygamy: History and Theology, 3 vols., Salt Lake City: Greg Kofford Books, 2013.