Study of the American relationship between church and state tends to focus either on the founding period or the modern era. Steven Green argues that a crucial development occurred during the 19th century: a "second disestablishment." By the early 1800s, formal, political disestablishment had occurred nationally and among the states. Yet America remained a Christian nation. In the 19th century, legal and educational reforms and a growing appreciation of the nation's religious diversity led to a second disestablishment. Green shows that the second disestablishment is the missing link between the Establishment Clause and the modern Supreme Court's Church/State decisions.