America has probably supplied the world with more new religions than any other nation. Since the first half of the 19th century, the country's atmosphere of religious experimentation has produced dozens of movements, from Mormonism to a wide range of nature-based practices grouped under the name Wicca.

By 1970 the religious scholar Jacob Needleman popularized the term "New Religious Movements" (NRM) to classify the new faiths, or variants of old ones, that were being embraced by the Woodstock generation....