A former Mormon acquaintance of mine from Ireland recently claimed that, between 1843 to 1904, the LDS Church taught that polygamy was necessary for exaltation. Here is my brief response to him; I am repeating it here as it is a very common claim.
The claim that even between 1843 to 1904 that “polygamy was necessary for exaltation” is refuted when one examines the sources. For instance, note the following from Wilford Woodruff:
I attended the school of the prophets. Brother John Holeman made a long speech upon the subject of Poligamy. He Contended that no person Could have a Celestial glory unless He had a plurality of wives. Speeches were made By L. E. Harrington O Pratt Erastus Snow, D Evans J. F. Smith Lorenzo Young. Presidet Young said there would be men saved in the Celestial Kingdom of God with one wife with Many wives & with No wife at all. (Wilford Woodruff's Journal, 9 vol.; 6:527, journal entry for 12 Feb. 1870 [The New Mormon Studies CD-ROM]).
Brigham Young stated that one must accept plural marriage to have been divinely revealed as a practice, notice the phrase "you will be polygamists at least in your faith" from a sermon from 19 August 1866, again, within your timeline:
*We wish to obtain all that father Abraham obtained. I wish here to say to the Elders of Israel, and to all the members of this Church and kingdom, that it is in the hearts of many of them to wish that the doctrine of polygamy was not taught and practiced by us...It is the word of the Lord, and I wish to say to you, and all the world, that if you desire with all your hearts to obtain the blessings which Abraham obtained, you will be polygamists at least in your faith, or you will come short of enjoying the salvation and the glory which Abraham has obtained. This is as true as that God lives. You who wish that there were no such thing in existence, if you have in your hearts to say: "We will pass along in the Church without obeying or submitting to it in our faith or believing this order, because, for aught that we know, this community may be broken up yet, and we may have lucrative offices offered to us; we will not, therefore, be polygamists lest we should fail in obtaining some earthly honor, character and office, etc,"—the man that has that in his heart, and will continue to persist in pursuing that policy, will come short of dwelling in the presence of the Father and the Son, in celestial glory. The only men who become Gods, even the Sons of God, are those who enter into polygamy.[1] Others attain unto a glory and may even be permitted to come into the presence of the Father and the Son; but they cannot reign as kings in glory, because they had blessings offered unto them, and they refused to accept them* (JOD 11:269; emphasis added)
In other words, one does not have to engage in plural marriage; one only has to accept the validity of it being revealed as a commandment of God [though to engage in such if/when commanded to do such] (see D&C 132).
Brian Hales, a leading expert on early LDS polygamy, further refutes this claim (often repeated by Fundamentalists and very ignorant critics) at:
Note:
[1] While one may be tempted to take the final sentence as definitive proof that only those *engaged* in polygamy (or, to be more correct, polygyny) will be exalted, one would be guilty of eisegesis of this sentence from the context, including Brigham's own qualification about those who will inherit the promises of Abraham (cf. D&C 132:30-31, 33-34, 37), wherein the membership of this taxonomy is extended to those who (1) accept the commandment to engage in polygyny to be divinely revealed without being expected to practice it (2) and those who, alongside accepting it being divinely sanctioned, engage therein.
[1] While one may be tempted to take the final sentence as definitive proof that only those *engaged* in polygamy (or, to be more correct, polygyny) will be exalted, one would be guilty of eisegesis of this sentence from the context, including Brigham's own qualification about those who will inherit the promises of Abraham (cf. D&C 132:30-31, 33-34, 37), wherein the membership of this taxonomy is extended to those who (1) accept the commandment to engage in polygyny to be divinely revealed without being expected to practice it (2) and those who, alongside accepting it being divinely sanctioned, engage therein.