By the 2009 Yearbook of American and Canadian Churches of the National Council of Churches, the Roman Catholic Church is the largest single denomination with a membership of 67,117,016, and Southern Baptist Convention ranks second at 16,266,920. Due to its large population, the United States has more Christians than any other country in the world. However, other countries have hi^ier percentages of Chrisdans out of their total populations.

Despite its status as the most widespread and influential religion in the US, Christianity is undergoing a continuous relative decline in demogr^)hics. While the absolute number of Christians rose from 1990 lo 2008 as the overall population increased, the actual percentage of Christians dropped from 86.2% to 76.0%. A nationwide telephone interview of 1,002 adults conducted by The Bama Group found that 70% of American adults believe that God is “the all-powerful, all-knowing creator of the universe who still rules it today,” and that of all American adults and 0.5% young adults hold to what the survey defined as a "biblical worldview"

The numbers of Catholics has grown over the country’s history，primarily through immigration and secondarily, in the 19th century, throu^i the acquisition of territories (once possessions of Francc, Spain, and Mexico) with predominately Catholic populations. It is now the largest Christian church in continental United States today. With about 70 million registered residents professing the faith in 2008，the United States has the fourth largest Catholic population in the world after Brazil, Mexico and the Philippines.

The 2008 Yearbook of American and Canadian Churches, a statistical listing of major religious bodies published by National Council of Churches, reports over 67,515,000 registered members of the Catholic Church. The next largest Christian group is a Protestant denomination, the Southern Baptist Convention, which reports 16,306,246 members.

A 2001 survey directed by Dr. Ariela Keysar for the City University of New York indicated that, amongst the more than 100 categories of response, “no religious identificationM had the greatest increase in population in both absolute and percentage terms. This category included atheists, agnostics, humanists, deists, and others with no theistic religious beliefis or practices. Figures are up from 14.3 million in 1990 to 34.2 million in 2008, representing a proportionate increase from 8% of the total in 1990 to 15% in 2008. Another nation-wide study puts the figure of unaffiliated persons at 16.1%.

In a 2006 nationwide poll, University of Minnesota researchers found chat despite an increasing acceptance of religious diversity, atheists were generally distrusted by other Americans, who rated them below Muslims, recent immigrants and other minority groups in “sharing their vision of American society' They also associated atheists with undesirable attributes such as criminal behavior, rampant materialism, and cultural elitism.

After Christianity and no-religion, Judaism is the third-largest religious affiliation in the US, though this identification is not necessarily indicative of religious beliefs or practices. Jews have been present in what is now the US since the 17th century, though large scale immigration did not take place until the 19th century, largely as a result of persecutions in parts of Eastern Europe. The CIA Fact Book estimates 1% of Americans belong to this group. Approximately 25% of this population lives in New York City.

A significant number of people identify themselves as American Jews on ethnic and cultural grounds, rather than religious ones. For example, 19% of self-identified American Jews believe God docs not exist, notwithstandii^ God’s existence to be integral to Jewish religious beliefs. The 2001 ARIS study projected from its sample that there are about 5>3 million adults in the American Jewish population: 2.83 million adults (1.4% of the U.S. adult population) are estimated to be adherents of Judaism; 1.08 million are esdmated to be adherents of no religion; and 1.36 million are estimated to be adherents of a religion other than Judaism.