They [Rappites] were moving from Southern Indiana to Pennsylvania, where they had originally settled when they came from Germany. They were looking for someone who wanted to buy a pre-built town, which wouldn't have been appropriate for any kind of normal settlement. That's when Robert Owen [Welsh industrialist and utopian socialist] buys the village and founds New Harmony.

So there's that change of general consciousness, and then there's this boom after the war, this expansion into the West. It was like the 1950s. The American economy was pumping at top speed. The kinds of people who would move into these communities and organize their lives around a utopian dream now had dreams about the West.

Utopian fiction is really boring. I had to read a lot of it, and it's not that much fun. But they're fascinating to me as historical documents. Cabet [Icaria's founder and author of the utopian novel, Travels in Icaria], is writing in the 1830s, and his idea of the perfect society reveals a lot about his time. But his book is uniquely bad.

One of the things that's amazing about reading the private writing of these folks is that they enthusiastically describe things which we have now seen, and which are widely regarded as unappealing. They'll write, "It's going to be beautiful, we're going to have a town of 1,000 stone buildings that are all identical." And we as modern readers think, we've seen that; that's bad Soviet architecture or a public housing project. Nobody fantasizes about living there.

There are Harvard grads, free thinkers, feminists, abolitionists, well-to-do people who want to go write poetry and live on a farm and cook and laugh and have a good time. As they themselves described it, it was an "inward facing" community. They were focusing on making a better existence for themselves, which I think is also the driving force of 20th century communalism in the US, the thought being that the world is corrupt, and we're going to build this little garden of innocence.

That to me was one of the most exciting, and weird puzzles of this book: how are the most religious people and the least religious people of their time all drawn to very similar visions of utopia?

I worry that I may have overstated the impact of Civil War on the utopians. By the time the Civil War comes, most of the communities were quite separated from the wider American society. Their rhetoric is still about transforming the world, but they're not having that much traffic with their neighbors.