It’s hard to piece together, with any certainty, exactly how many (if any) plural wives Joseph Smith had before 1841. He had learned the doctrine of plural marriage as early as 1831, see, e.g., the heading to D&C 132, but he was very reluctant to practice it, and may have even hoped that it would be a principle he could “restore” as an ancient truth without having to actually practice it.
The most credible probability is, in my opinion, that Joseph took only one plural wife (Fanny Alger), before 1841. And the experience seems to have confirmed all of his worst fears about plural marriage. His reputation was tarnished, Emma was incensed, close friends apostatized, and the marriage itself was apparently an abject failure: Instead of going to Jackson County, Missouri with her uncle as Joseph hoped, Fanny left Kirtland with her parents, and in Indiana, she met and married Solomon Frank Custer. To this day, Fanny Alger does not appear on the records of the church as one of the dozens of women sealed to the prophet Joseph Smith (interestingly, she has since been sealed by proxy to Mr. Custer). Even more curiously, the family did not leave Kirtland on bad terms with Joseph Smith. Fanny’s parents moved on to Nauvoo, and eventually followed Brigham Young to Utah.