One man changed the face of America after eight years in power. Without doubt, that man is outgoing President Barack Obama.

There were many cultural, technological and social changes that happened in the world's only superpower from 2008 to 2016, but the biggest of them all happened in the faith front, according to the latest study by the Pew Research Center.

For the first time in its history, with Obama at the helm and providing guidance, America saw a drastic decline in the faith and religion of its people.

"When it comes to the nation's religious identity, the biggest trend during Obama's presidency is the rise of those who claim no religion at all," Pew president Michael Dimock pointed out. "Those who self-identify as atheists or agnostics, as well as those who say their religion is 'nothing in particular,' now make up nearly a quarter of the U.S. adult population, up from 16 percent in 2007."

In an earlier study conducted in 2015, Pew showed major shifts in Americans' religious affiliations from 2007 to 2014. The study showed that the number of self-described Christians went down from 78 percent to 71 percent.

The numbers also plummeted in such categories as belief in God, daily prayer and religious attendance. For instance, the Pew study showed that church attendance went down by three percentage points, from 39 percent in 2007 to 36 percent in 2014. Belief in God also fell, from 92 percent to 89 percent.

The only consolation was that the "large majority of Americans who do identify with a faith are, on average, as religiously observant as they were a few years ago, and by some measures even more so," according to Dimock.

Coupled with the erosion of faith was the surge in the public acceptance of same-sex marriage and marijuana, which is still considered an illicit drug in most U.S. states. However, during Obama's eight years in power, marijuana use was legalised in eight states and the District of Columbia.

Majority of Americans have also accepted gay marriage, which is now legal throughout the United States after the U.S. Supreme Court made a landmark ruling in 2015 legalising same-sex union. That decision stunned the Christian community, with many of the largest religious institutions in America firmly opposing it on the ground that marriage is only for a man and woman as clearly defined in the Bible.

However, the issue has caused a rift among Christian denominations as some groups decided to allow same-sex couples in their congregations to marry. These groups include the Presbyterian Church (U.S.A.), the Episcopal Church, the Reform and Conservative Jewish movements, the Unitarian Universalist Association and the United Church of Christ, according to a December 2015 Pew study.