Historian Kevin Kruse explains how his sources surprised him and forced him to set his story earlier than he had planned:

When I began this project more than a decade ago, I set out to explore the roots of the Religious Right in the 1960s and 1970s …

But where to begin? In the conventional narrative on the Religious Right, popular outrage over the Supreme Court’s 1962 decision against state-mandated school prayer represented the earliest rumblings of modern religious conservatism. Accordingly, I traveled to the Library of Congress to conduct research in the papers of Justice Hugo Black, the jurist who authored that decision. I was delighted to find ten boxes filled with angry letters, telegrams and petitions he’d received about the ruling, but surprised at what I discovered in them …

These stacks of letters sent to Justice Black showed these religious slogans did have real meaning. In the eyes of ordinary Americans, I soon realized, the “ceremonial” nature of things like the pledge of allegiance and the national motto did not diminish their importance. Quite the contrary, it vested them with incredible weight. The official embrace of religious slogans by their government seemed as politically significant and legally binding to them as any formal amendment to the Constitution.

As an historian, that sort of moment – when the archives surprise me so thoroughly – is the surest sign that I’ve stumbled onto something important. Accordingly, I changed my plans. Rather than focus on grassroots conservatism in the 1960s and 1970s, I decided to explore the rise of this religious nationalism in the 1950s.

This is a common hazard of historical research: you want to write about one period, but find that the events of that period can only be understood in reference to earlier events. So we beat on, boats against the current, borne back ceaselessly into the past.