While it is true that as you say that “plural marriage [was] a divine mandate from God, [and] a good wise and holy practice,” it was also more than a “social practice.” Doctrinally speaking, plural marriage was encapsulated in the same revelation (D&C 132) that set forth the eternal Gospel laws where all “covenants, contracts, bonds, obligations,” etc. (verse 7), and in particular, the marriage covenant, may be sealed and in force after the obliging parties are dead. That plural marriage would be so intimately associated with this sealing power (“And again, as pertaining to the law of the priesthood” — verse 61) binding such covenants after death and for eternity, unavoidably makes plural marriage the marriage order of the heavens. Indeed, the metaphor taught to me at the tender age of 16 at the Orem High School seminary in 1969 by Brother Dale C. Mouritsen was that “If Heavenly Father’s wives were all lined up side to side, mortal eyes couldn’t see the other end.” If that is true, then “celestial” plural marriage is the pre-existant environment we all grew up in, as spirit children. Most of my four seminary teachers also taught us that plural marriage was to return in the end times, as it was necessary to be practiced in the Millennium. This is also something that Bruce R. McConkie taught in Mormon Doctrine, which concept caused little alarm among the people I knew growing up in Utah in the 1960s. That was just the “way it was.”

As for “Mormons today honor[ing] their polygamous ancestors and declar[ing] that there was no ‘mistake’ about it,” I submit that depends on who you talk to. I agree that formally, the LDS Church has made no outward declaration that plural marriage was a “mistake,” and that there are many Mormons today who do honor their polygamous ancestors as you say, but I can also say from personal experience that many LDS members I’ve spoken with are greatly reluctant to consider plural marriage in the positive manner than you have described it: “a divine mandate from God, [and] a good and wise and holy practice;” in fact, several have personally expressed to me their belief that it was indeed a “mistake,” or at best an difficult-to-tolerate accommodation due to an alleged superfluity of women – a notion refuted by John Widstoe in his book Evidences and Reconciliations (pp. 390-391).

As for 1890 being the year that “ended polygamy,” we have in our family records a “separation of property” agreement between my maternal great-great grandfather and my great-great grandmother, where he chose to live intimately only with his other wife starting at that time. What was the date of this legal instrument? 1889. So did my ancestor give up polygamy because of the Manifesto? Not if it hadn’t been issued yet. Most likely it was due to the danger of being turned in by the “skunks” as they called them then, who would betray their neighbors to the federal marshals. I was quite surprised when I saw the date, as our family oral traditions had it that he had responded to the clarion call from Salt Lake to abandon the practice, which ostensibly would have been 1890.

As for it taking “a few years to wean people away from plural marriage,” the only minor caveat I submit there is to question just who these people were who had a difficult time being “weaned.” I was shocked to learn back about 1985 in our ward in Tempe, Arizona (I was stationed in Arizona then while in the Air Force), where our Sunday School gospel doctrine teacher (from Kanab), in Gospel Doctrine class, instructed his class (and this was the first time that I had heard this) that it did take a while for some to be “weaned” from taking new plural wives after 1890, and for other authorities to be “weaned” from performing such ceremonies. Most shocking of all to me, and it took a while to come to terms with it, was how he informed us that Wilford Woodruff himself married another wife several years after 1890. I assure you that all present that Sunday were members in good standing, and nobody went screaming to the Bishop. I suppose that President Wilford Woodruff could technically be included the term “people,” but being the President of the Church would seem to give him a bit more stature than that.

My great-grandfather Helaman Pratt married his third wife in 1898, and he was one of the leading Priesthood holders in the Mexican colonies, under Anthony Ivins. We have no family record of my grandfather (Rey L. Pratt) having married plurally, but Rey Pratt’s name appears immediately after Helaman Pratt’s name in a list of over 200 LDS men claimed in a 1910 Salt Lake Tribune “exposé” to have married a plural wife after the manifesto. But there is precedent for such things, without even such a man’s children being aware of it. My grandfather Rey Pratt was also a leader in the Mexican colonies, a missionary nearly his whole life, and who became one of the Seven Presidents of Seventy back in Salt Lake City, a few years before he died in 1931. When I taught at the MTC many moons ago, I enjoyed visiting one of the brand new missionary dorms just named after my grandfather, “Rey L. Pratt Building.” There was another dorm named after Helaman’s father, my ancestor Parley. But then I suppose Helaman Pratt and Rey Pratt are more easily described as “people” than the Church President.

Overall, a good reply. I hope you will pardon the rambling of a semi-old coot.