What really fascinates me is the idea of liminality: the joining together of two very different states. You have a kind of intensification of knowledge and emotion. The Transcendentalists were fascinated by cemeteries, and I'm fascinated by the same things: the coming together of these disparate states of life and death, nature and culture. Cemeteries are the places that those kinds of meetings of the past and the future come to the fore.

How are these tensions reflected in the design of cemeteries?

Burial isn't just about celebrating the dead. It's about containing the dead—keeping them out of the realm of the living, which is why cemeteries were removed from cities. We would like to go into their world when it's convenient for us. Look at themes in popular culture, at how often the worlds of the living and dead intersect and how disastrous that often is. Think of zombie movies—havoc usually ensues.

Particularly in the great 19th-century cemeteries and as well in the 20th-century cemeteries, one of the great features is the entrance gate. Very elaborately fashioned, it marks the fact that you're leaving the mundane world behind. Another way it has played out is that American cities are gridded cities. Cemeteries operate as alternate cities—cities of the dead. They are often very complex.

Cemeteries we built for ourselves, increasingly after 1830, were places with winding roads and picturesque vistas. The idea being that you leave behind the mercantile world outside the gates and enter into the space where you can meditate, where you can come into contact with spirituality and concentrate. They were quite important spaces for recreation as well. Keep in mind, the great rural cemeteries were built at a time when there weren't public parks, or art museums, or botanical gardens in American cities. You suddenly had large pieces of ground, filled with beautiful sculptures and horticultural art. People flocked to cemeteries for picnics, for hunting and shooting and carriage racing. These places became so popular that not only were guidebooks issued to guide visitors, but also all kinds of rules were posted.

In the book, you note that cemeteries as we know them today first emerged in the 1830s, with the rural cemetery movement. As you mention, Americans had always buried their dead, but did so in churchyards, town commons, or municipal burial grounds. Why the shift to these larger cemeteries?

The old church burial grounds were beginning to be seen as inadequate, dangerous, crowded, expensive to maintain, and as carriers of disease. Thousands of burials had taken place on very small plots of ground; these places filled up. You often had burials five or six coffins deep. Sometimes the walls would break down during floods—it was actually rather horrible—coffins would break open and bodies would spill out into the street. During times of epidemics—yellow fever, cholera—cemeteries were seen as centers for the gathering of these diseases and their dissemination. At the same time, cities are becoming more crowded, real estate prices are rising. As the economy was growing, it also came to be the fact that Americans wanted to provide better amenities for their citizens. Cemeteries were seen as the last great necessity. By moving the dead out of the city center to places like Brooklyn and Cambridge, these "rural cemeteries" allowed for much larger burial grounds that also removed the dead from the immediate realm of the living.