<P> The United States federal government was the first national government to have no official state - endorsed religion . However, some states had established religions in some form until the 1830s . </P> <P> Modeling the provisions concerning religion within the Virginia Statute for Religious Freedom, the framers of the Constitution rejected any religious test for office, and the First Amendment specifically denied the federal government any power to enact any law respecting either an establishment of religion or prohibiting its free exercise, thus protecting any religious organization, institution, or denomination from government interference . The decision was mainly influenced by European Rationalist and Protestant ideals, but was also a consequence of the pragmatic concerns of minority religious groups and small states that did not want to be under the power or influence of a national religion that did not represent them . </P> <P> The most popular religion in the U.S. is Christianity, comprising the majority of the population (70.6% of adults in 2014). According to the Association of Statisticians of American Religious Bodies newsletter published March 2017, based on data from 2010, Christians were the largest religious population in all 3,143 counties in the country . Roughly 46.5% of Americans are Protestants, 20.8% are Catholics, 1.6% are Mormons (the name commonly used to refer to members of The Church of Jesus Christ of Latter - day Saints), and 1.7% have affiliations with various other Christian denominations . Christianity was introduced during the period of European colonization . </P> <P> According to a 2012 review by the National Council of Churches, the five largest denominations are: </P>

What is the largest religion in the us