The Nashville, Tennessee-based group started the tradition more than a century ago. As official history tells it, the genesis of the Gideons strikes a familiar religious theme: There was not enough room at the inn. Two men, John Nicholson and Samuel Hill, had to bunk in a double room at the overcrowded Central Hotel in Wisconsin in 1898. They discovered their shared faith, decided to start an association of Christian traveling salesman and, in 1908, the group adopted a plan to supply Bibles to every hotel room in the United States.
Since then, the organization has distributed more than 2.4 billion Bibles and Testaments around the world in hospitals, prisons, schools and, yes, hotels.
But according to the STR survey, conducted every two years in coordination with the American Hotel & Lodging Association, the numbers have been on a downward trend. In 2008, for example, 84% of rooms had religious materials, a number that had fallen to 69% in 2016 before dropping further two years later. Figures have fluctuated over the years because of incomplete reporting, but the research company says the historical data in the latest numbers is the most accurate.
Industry experts say hotels are reconsidering most of what they put in rooms - including the very night tables that typically house Bibles - based on what guests say they want.
"They are doing a better job of identifying the mission-critical amenities," says Mehmet Erdem, who teaches hotel operations and information technology at the University of Nevada at Las Vegas.
And in an era where hotels are expected to provide free, fast WiFi, and phones can summon information in seconds, a hard copy of a book might not be all that necessary.
"I'm thinking that technological advances will further reduce the number of Bibles in hotel rooms," says Stanley Turkel, a consultant who has written books about hotel history. "What will be the subsequent technological advance after iPhones, I cannot predict. It's not going to be Gideon Bibles in guest rooms."
Most large hotel chains, including Hyatt, Hilton and InterContinental Hotels Group, leave it up to the owners and operators of individual properties to decide if they want to place religious reading materials in their rooms.
But hospitality giant Marriott International is a notable exception. The company requires almost all of its 30 brands - including those that were once part of Starwood Hotels & Resorts - to place the Bible and Book of Mormon in its rooms.
"Providing the Bible and Book of Mormon in guest rooms has been a company tradition since Marriott entered the lodging business more than 50 years ago," spokeswoman Connie Kim said in an email. "They are there for guests to read and take if they like."
Two of the company's newer, hipper brands are exempt from that requirement: the millennial-aimed Moxy and Edition, a lifestyle brand in partnership with Ian Schrager.
Some newer brands also targeted to young, modern travelers are taking the same approach. CitizenM, a 12-year-old company with 20 locations around the world, does not put religious texts in rooms. Neither do the trendy Freehand and Generator brands, which together have 19 locations.
"The concept of putting a Bible in-room is an outdated practice and is exclusive to the religious denomination that believes in that scripture only," Alastair Thomann, CEO of Generator and Freehand Hotels, said in an email. "We don't provide Bibles in-room because our travelers are so diverse, and we want our properties to feel inclusive of all varying beliefs and spiritual traditions."
Even some older names - the Borgata in Las Vegas and Travelodge UK - were ahead of the secular pack. Travelodge UK moved Bibles from rooms to the reception desk back in 2007 "in order not to discriminate against any religion," according to a statement.
Provenance Hotels, with 14 properties in the United States, offers guests a "spiritual menu" in their rooms that lets them call the front desk and request the book of their choice. The company introduced the option more than a decade ago "to recognize and honor the diversity of our guests who hail from a myriad of cultural and religious traditions," spokeswoman Kate Buska said in an email.
"The Bible is, of course, an option, but rather than offer a one-size-fits-all approach of placing just that book in the nightstand, we wanted to give our guests options so we can deliver inspiration tailored to the individual," she said.
That solution is welcomed by the Freedom From Religion Foundation, a Wisconsin-based organization that promotes church-state separation and embraces nontheism. The group regularly asks hotels to remove religious literature from rooms when they have conventions and sells $3 stickers - "perfect for hotel rooms" - with a skull and crossbones that say "Warning: Literal Belief in this book may endanger your health and life."
The foundation has sent letters over the years to hospitality companies asking them to offer "Bible-free rooms" to be more hospitable to guests who aren't religious.
"We don't want to pay high prices to rent a room and then find this sometimes open Bible when we go to open the drawer . . . and be confronted with this book that is so primitive and very anti- our rights," says Annie Laurie Gaylor, one of the foundation's presidents.
The group hasn't asked hotels to stop offering the material altogether - just to keep them available outside the room.
"Start a little library so people could come and get it," Gaylor says. "We hope that you will include perhaps the work of [evolutionary biologist] Richard Dawkins and nonbelievers as well."