A previous version of this story misstated the percentage of people in the 2015 Gallup poll who identified as Christian. The story has been corrected.

If you don’t believe in God, you might want to move to the Pacific Northwest.

Portland, Ore., San Francisco, Calif. and Seattle, Wash. are tied on a 2015 list of metropolitan areas with the most religiously unaffiliated residents (37%), according to the nonpartisan and nonprofit Public Religion Research Institute’s American Values Atlas, a survey of 50,000 people. Seattle and San Francisco have more religiously unaffiliated people than the previous year (33%), while Portland has less religiously unaffiliated residents than 2014 (42%). Las Vegas and Denver were next on the list with 29%.

On the other end of the spectrum, Charlotte, N.C. was the metropolitan area with the fewest people without any religious affiliation (16% in 2015 versus 17% the previous year), followed by Dallas, Texas and Milwaukee, Wisc. (17% in 2015) and Houston (18%) and Kansas City (19%).

Some important caveats: The AVA survey didn’t specify that a certain percentage of these metro areas were atheists. While many people who don’t believe in God may not attend religious services, there are (of course) faith traditions such as Unitarian Universalism that welcome and include humanists and atheists; many people who might not believe in God may just as likely go to church for spiritual reasons too, or merely because they like it.

Why the regional differences? “Portland is quirky and different, and very attractive to people who may not feel comfortable in other social environments, particularly with a stigma against those who are atheists,” says Daniel Cox, research director at the Public Religion Research Institute. In fact, “The Big Sort,” a 2008 book by Bill Bishop, documented the “clustering” of like-minded Americans around politics and culture. While 93% of people said they would vote for a Catholic for president and only 6% say they would not, 58% said they would vote for an atheist while 40% said they would not, a nationwide 2015 Gallup survey found.

“The strong religious culture in the South reflects a variety of factors, including history, cultural norms and the fact that these states have high Protestant and black populations — both of which are above average in their self-reported religious service attendance,” according to a separate Gallup survey of over 177,030 U.S. adults last year on church attendance. And 10 of the 12 states with the highest self-reported religious-service attendance are in the South, along with Utah and Oklahoma. (Utah ranked as No. 1 because of the 59% Mormon population there, and Mormons have the highest religious attendance of any major religious group in the U.S.)

Also see: Americans are giving less money to God

This was not the case in the Pacific Northwest. A 2004 book, “Religion and Public Life in the Pacific Northwest: The None Zone,” found that there was no influx of one major denomination there, so religious groups, spiritual environmentalists, and secularists “must vie or sometimes must cooperate” with each other to address the region’s pressing economic, environmental and social issues. “A clearly recognizable religious reference group functions as a social mirror, alongside or against which an individual can define himself or herself. The Pacific Northwest has neither,” the writers concluded, adding, “Most people who come into the region do not come seeking to replicate what they left behind.”

Overall, one-fifth of the U.S. population has no religious affiliation whatsoever, studies show. Some 17% of Americans said they had no religious affiliation, according to research published last year by polling firm Gallup, up from 16% the year before and 10% a decade ago, and up from 1% in the 1950s. The Gallup polling concludes that 38% of people identify as Protestant, 9% as Christian, 23% as Catholic, 2% as Jewish and 2% as Mormon, 6% gave “other” as an answer, while another 4% gave no answer to the question, and 17% answered “none.”

How Americans feel about religious groups also varies, influenced in part by the religious demographics of the rest of the population, according to a 2014 survey of over 10,000 adults by Pew Research Center. On a rating from zero to 100 — where zero reflects the coldest, most negative possible rating and 100 the warmest, most positive rating — Jews received 63%, the most positive rating, followed by Catholics, at 62%, and evangelical Christians, at 61%. Buddhists received a 53% rating, while Hindus received a more neutral 50% and Mormons 48%. Atheists and Muslims received just 41% and 40%, respectively.

Read: How much should I give to the church collection plate?