“I really just like finding the actual people and telling their stories,” Vowell says. “It always bothers me when the Puritans are lumped together in some big, bland stereotype.” A longtime contributor to public radio’s This American Life, Vowell, 39, isn’t interested in sociology, but rather in “resurrecting the dead.” In The Wordy Shipmates (due in October from Riverhead), she explores the influence of Winthrop and his contemporaries, including Roger Williams, on our current society. She aims to explain how, as a nation, we’ve inherited the Puritans’ notion that we are God’s chosen people. “The thing I always loved about Winthrop’s sermon was how it’s a poem of community,” says Vowell. She is drawn to the idea that “we should labor together, mourn together and suffer together.” After 9/11, Vowell, who lives in Manhattan, found comfort in Winthrop’s idea that we should be members of the same body. “That’s what it felt like to be in New York, because we were literally breathing bodies. It was so very intimate.”

As she’s made the switch from personal to historical essays—prompted by a 1998 radio documentary she made with her twin sister, Amy, about the Trail of Tears, the 1838 forced relocation of the Cherokee Indians—Vowell notes that some readers have dropped off, but that she’s picked up new ones. “Whatever variation of younger liberal person and older Republican dad: mine are books they have in common.”

Vowell looks for the humor in every story (“I have a little of the Jackass entertainer in me”) and found plenty to amuse herself reading through the letters and papers of Winthrop and other puritans. For her previous book, 2005’s Assassination Vacation (Simon & Schuster), Vowell traveled the country in search of sites and obscure memorabilia related to various presidential assassinations and assassination attempts. This time around, her travels were confined mostly to Boston—which she calls the “Grand Canyon of history, with one layer of sediment after another”—where she read original documents at the city’s Massachusetts Historical Society.

One of the figures who caught her attention was theologian Roger Williams, Winthrop’s frequent verbal sparring partner and eventual founder of Rhode Island. He was, according to Vowell, “a weirdo.” Williams particularly interested Vowell because “he figured out—and this is one of the most pressing questions of our time right now—how to remain a religious fanatic and live in the world without killing other people.” Williams also vehemently argued for the separation of church and state, but, as Vowell points out, for the opposite reason than Thomas Jefferson would 150 years later: “Williams thought once the state is sponsoring the church, the church will get caught up in state-sponsored violence, and he didn’t find that particularly Christian.” On the whole, Vowell tells me, “Williams was a nonviolent fanatic, which is all anyone asks of any fanatic.”

Another inspiration for the book came after she watched Ronald Reagan’s 2004 funeral on television, when Winthrop’s sermon was quoted several times. “I grew up during the Reagan era,” says Vowell, “and 'city on a hill’ seemed to be the national catchphrase, and the idea that Reagan took from the sermon was the same one everyone else does: we’re a beacon of hope.” What the collective American consciousness has neglected to absorb from Winthrop was the sense of foreboding. For the Puritans, “there’s this utter and total terror of their God because they know if they fail—even though they were chosen for greatness—the punishment will be severe.” Winthrop, Vowell says, continually returned to the biblical passage from Luke, where great power came with great responsibility. “It seems like the United States skimmed off the top and took the good parts,” says Vowell. “We have this tendency to look on the bright side and the way we use rhetoric to do that is our greatness and our downfall.”

Sarah Vowell has always been fascinated by John Winthrop, one of the first settlers in the Massachusetts Bay Colony and the author of the Model of Christian Charity sermon that Ronald Reagan mined for his “city on a hill” slogan.