In the United States, the First Amendment to the Constitution (1791) prohibits the federal government from establishing or prohibiting a religion, and in 1947 the U.S. Supreme Court ruled that states cannot create established state churches in Everson v. Board of Education.
^Roger Williams, James Calvin Davis (editor), On religious liberty: selections from the works of Roger Williams, (Harvard University Press, 2008), ISBN0-674-02685-3, ISBN9780674026858[1](accessed July 11, 2009 on Google Books)
^James Emanuel Ernst, Roger Williams, New England Firebrand (Macmillan Co., Rhode Island, 1932), pg. 246[2]