Where did fundamentalist polygamy in America begin? Polygamy isn't new. Until the 20th century, more than two-thirds of the world's population allowed polygamous marriage. But polygamy among Christians in the United States of America presents an anomaly. Polygamy as part of a religious belief began among members of The Church of Jesus Christ of Latter-day Saints in the early 1840's, when the founder and prophet, Joseph Smith, Jr., quietly spoke to a few of his closest associates concerning a revelation he said he'd received instructing him to initiate "The Principle of Plural Marriage." Some historians speculate that without the quantum leaps of population made possible by polygamy, the Latter-day Saints would not have survived losses incurred during the raids by mobs, the exposure of Winter Quarters, and the trek across the Great Plains, not to speak of the 500-man Mormon Battalion mustered to fight the Mexican War, in addition to other casualties of the Old West. The Church continued the practice until 1890, when political and legal pressure to give up polygamy reached a fevered pitch, and the LDS Church passed a manifesto to end it.
Fundamentalists believe that God does not change and insisted that "the Principle" is an eternal law lived by exalted beings. But members in good standing of the LDS Church agree that the obligation to live polygamy has been removed and, in fact, is cause for excommunication.
To fundamentalists who insist that "God does not change," I'd point out that the Creator of All formed Canada geese to be polygamous during times of disease and sparse population, monogamous during times of balance, and homosexual during times when the population outstrips food availability. I suspect that God can collude with Nature to do whatever needs to be done to make life work. What do you think?