Historian Benjamin Park, an assistant professor of history at Sam Houston State University, has written a compelling and accessible history of Mormonism in the 1840s. “Kingdom of Nauvoo: The Rise and Fall of a Religious Empire on the American Frontier” comes out Tuesday from W. W. Norton’s Liveright imprint, and I recommend it to anyone who wants to better understand Joseph Smith, polygamy, politics and how profoundly this chapter of Mormon history affected everything that came after.

This interview has been edited for length and clarity:

RNS Why do we need this book? What should people understand about Nauvoo and Mormon history?

Park • The easy answer is that there hasn’t been a book written on Nauvoo for a general audience outside the LDS faith for over 50 years, and that seemed to me a glaring hole. Part of that is because most people see early Mormonism, including Nauvoo, as an outlier. The idea is that those people are the “crazies,” so they’re not included in the larger story. One of my goals is to show that Nauvoo reflects larger parts of American religious history, and more importantly, that it shows that democracy has not always been a safe or assured idea in America.

RNS • How did early Mormonism test the boundaries of democracy?

Park • Especially on the frontier, democracy often translated into peer majority rule. That’s very clearly democratic — the base idea is that two people outvote one person — but what happens when the majority want to oppress the minority?

In Nauvoo, you see the conflict. The Mormons who gather in Nauvoo think democracy failed them, that their rights as a minority group had not been respected in Missouri, where they had lived previously. And so they take measures to save what they believe to be their religious rights, including voting as a united bloc, organizing a city militia, and interpreting laws in a way that empowered Nauvoo’s municipal court. However, those actions prompt the people who live around Nauvoo to think the Mormons are a direct threat to democracy and to their rights.

Democracy seemed to be so tenuous that if you get a group of people that’s large enough to have influence, but who refuse to play by the correct rules, the whole system falls apart. And so in the end you get both the Mormons and those who oppose them giving up on the democratic system and taking justice in their own hands.

RNS • I was intrigued to learn there was a period when the church was empowered to run the city but not to punish people for breaking the law. The only leverage they had at their disposal was excommunication from the church. So there’s a guy who gets excommunicated for operating an unauthorized ferry?

Park • Yes. Before the city charter, the church in Nauvoo is operating as a de facto government. However, once the charter is in place, then they have the ability to punish people through secular means, which allowed them to follow more traditional judicial methods.

RNS • Do excommunications go down then?

Park • No. Actually, the High Council, which prior to the City Charter is the most powerful group in Nauvoo, is ramping up its crusade at this time in 1841 and 1842, and one of the ways they do that is through policing morality, especially sexuality. So you get two different bodies exercising considerable authority at the same time.

RNS • This effort was spearheaded by Joseph’s brother Hyrum Smith, right?

Park • Yes. Two worlds are forming simultaneously: Joseph Smith is building this domestic experience, an expansion of the human family through polygamy. And Hyrum Smith, who does not yet know about polygamy, is building this large moral police force at the same time. Very soon these two worlds are going to collide, causing the city’s biggest crisis.

RNS • But there’s no permanent rupture between the two brothers.

Park • No. What happens is that when Hyrum Smith learns about polygamy in 1843, he suddenly and radically changes teams. And when he becomes a polygamist, he presents polygamy to the High Council. Yet these same men who had been working with Hyrum to root out sexual impropriety feel betrayed that he has changed sides. Some of those men become the core group that forms the Nauvoo Expositor [newspaper].

RNS • A lot of readers are going to be curious about polygamy in Nauvoo, and what your research has to say about Joseph Smith and plural marriage.

Park • One of the problems I have with the general literature is that the books that cover Nauvoo are either solely focused on polygamy, or they’re about everything else and don’t really deal with polygamy. What I found fascinating, digging into the topic, was how intertwined polygamy was with everything else going on in Nauvoo.

Perhaps in late 1840 or early 1841, Joseph starts teaching new things about the temple. Most of the LDS ideas about temples, sealings, bodies and eternity date from this period. Baptisms for the dead appear during this time. But it’s also during those months that Smith starts preaching and practicing polygamy. In fact, I had one of those awakening moments when I realized the most likely date for Joseph Smith’s first plural sealing was the night before the Nauvoo temple cornerstone ceremony.

RNS • What did you learn about polygamy that you didn’t know before?

Park • I learned that polygamy developed haphazardly over the final three years of Joseph Smith’s life. I think there’s sometimes an assumption that Joseph Smith either revealed or came up with the idea of polygamy as a strict set of ideas in early Nauvoo, and then they stayed pretty much the same until his death. But when doing the research, I realized that there were several moments of major transition in how polygamy was taught and believed and practiced.

I was also struck by how often women shaped how polygamy developed. For one example, Sarah Whitney, one of the teenage women who were sealed to Joseph Smith, pestered him for a written document assuring her and her family’s salvation. That ends up being one of the most important records we have for understanding how polygamy develops in 1842 and 1843. It’s the only document we have from Joseph Smith’s own hand about polygamy, and it remains in Sarah Whitney’s possession until she dies.

This is where we get the idea that if a couple is sealed, their entire family is sealed together. That idea is later preached by Orson Whitney, who is related to Sarah Whitney. Orson gives a General Conference address in 1929 saying that when a husband and wife are sealed, none of their family can be lost, and if any of their children leave the fold, the “divine tentacles” will pull them back in.

RNS • Finally, I want to ask about Joseph Smith’s death. The narratives about it are highly polarized.

Park • My primary goal in writing about Smith’s death is to try to explain why a group of American citizens decided that their only avenue to justice was to form a mob and kill someone who was already in state custody. To put it simply, Joseph Smith had found success in seemingly evading justice before through habeas corpus. Those outside of Nauvoo thought he had found a way to game the system, that the laws of a frontier society were pliable enough so that he would never be brought to justice. They also feared that politicians were unwilling to change those laws because they didn’t want to lose the Mormon vote.

On three separate occasions, then, there’s an arrest warrant for Joseph Smith, yet he finds a way to get off scot-free. So in June 1844, when he’s finally arrested and held in the county jail, his enemies say, “I’ve seen this movie before. The democratic system is not strong enough to hold someone who is such a threat to society.” And so they gather in the nearby town of Warsaw and form what they call a Warsaw Committee of Safety. And that was the same name — a “Committee of Safety” — that was used in the American Revolution. In their imagination it signified that sometimes, extralegal actions are necessary to preserve their rights.

This trial wouldn’t have had anything to do with Missouri; this time, he was arrested on charges of destroying the printing press for the Nauvoo Expositor, but that wouldn’t have been a major punishment. But when he turned himself in for public destruction of the newspaper, he instead was charged with treason for declaring martial law in Nauvoo in the week following the paper’s destruction. And treason carried a much more severe punishment.

RNS • What do you think would have happened at the trial if Joseph Smith had not been killed?

Park • There probably would have been a major court case. While I don’t know how it would have turned out, Joseph Smith did have powerful political friends, and the state likely would have been wary to take any radical actions for fear of reprisal from the Mormons. For example, even after the flurry of events in summer 1844, a slate of political candidates still courted Mormon votes in that August’s election.

RNS • Do you mean a reprisal at the ballot box, in that the Mormons would vote them out of office, or a violent reprisal from the armed Mormon militia in Nauvoo?

Park • Both. There would definitely be an electoral punishment, with the Saints no longer supporting those political parties. But there was also this constant fear of the Nauvoo Legion. Joseph Smith boasted he had 3,000 men who would muster at a moment’s notice, and that probably was not an exaggeration.

Illinois was often very reticent to convict people in controversial cases, as seen the next year when the people who killed Joseph Smith were let off free, and the Mormons who had engaged in some retaliating actions afterwards were all let off free.

RNS • Finally, what do you hope readers take away from your book?

Park • For those outside the LDS tradition, I hope that they see Mormon Nauvoo as an important episode in understanding America’s religious and political history, and that it highlights for them that our democratic system has not always been our most assured political philosophy. For LDS readers, I hope they are able to view Nauvoo, one of our most important periods, in a new light, one that is embedded within its surrounding culture.

In other words, I hope all readers come away thinking Nauvoo matters, perhaps for reasons they hadn’t considered before.