SEATTLE >> It’s the photo every tourist visiting Seattle has to have: the gum-wall selfie.

The quirky oddity at Pike Place Market, for years just 15 feet wide, has turned into a canyon of chewing gum.

Today, the gum wall is 8 feet tall and over 50 feet long — on both sides of the alley.

On a sunny weekend day, hundreds of people can be found crammed into Post Alley — chewing gum, blowing bubbles and documenting the entire experience.

Mika Liao was in the alley with three of her co-workers on a recent weekday. The four Taiwan residents were visiting Seattle on business. They had seen the gum wall on Instagram before leaving Asia and it was on their must-see list.

“It’s the top three: Pike Place market, first Starbucks, gum wall,” Liao said.

Space Needle? Passe.

The women were all holding Starbucks coffees as they stuffed gum in their mouths.

They were careful not to brush up against the multicolored wads of gum. “Everyone’s DNA is here,” Liao said. “Everywhere.”

She paused for a moment. “I’m going to leave my DNA here.” The women giggled.

Humble beginnings

The gum wall is perhaps Seattle’s purest, most interactive public art project. It began in the early 1990s outside the entrance to the Market Theater. Unexpected Productions had just rented the space.

“Our audience started that gum wall,” said Mary Bacarella, who volunteered to work the company’s books in the early 1990s.

“Our audience would line up on that wall, and I don’t know who started it, but they put a penny and a piece of gum on the wall,” Bacarella said.

The practice soon caught on and the gum wall was born.

The market asked the theater to clean the wall. They did.

“It immediately started up again,” she said.

After the third round of cleaning and gumming, the market management gave up and let the gum wall stay. Today, Bacarella, executive director of the Pike Place Market Preservation and Development Authority, is the management and decidedly pro-gum.

“You walk down the alley and you think a street fair is going on,” Bacarella said. “You see brides getting their picture taken in front of it, somebody doing a photo shoot.”

It’s not just gum stuck to the walls. Coins, spoons, notes and mementos are glued to the walls.

“C+M” is spelled out on the wall in gum. Nearby, “W+C” had declared their love as well.

Audrey Tewnion was standing in the alley with her 13-year-old daughter, Amy Cuthbertson, earlier this month, visiting from Vernon, British Columbia. Both were busy chewing gum.

“It’s one of the things that you always hear about, that you have to see,” Tewnion said. “It’s on Trip Advisor.”

“I’ve seen lots of pictures of it on Instagram,” Amy added. The #gumwall hashtag has more than 190,000 posts on Instagram.

But not everyone in the alley is a fan. Doug March is a bartender at the Alibi Room. The bar and restaurant’s entrance is in the middle of the alley.

“I find it disgusting,” March said.

When the wall suddenly exploded in popularity, the quest to keep gum from migrating to the other side of the alley where the Alibi Room is was futile, he said.

“They stuck signs up that said, ‘No gum,’ ” March said. “Those got covered up in gum.”

The Alibi Room does draw a line though — the wide brass panels that trim the entrance are completely gum-free. How often does it get cleaned?

“Every day,” March said in a resigned tone.

Cleaning

In 2015, market management became concerned about the potential damage to the historic brick walls, said spokeswoman Emily Crawford.

A literal ton of gum was cleaned off the wall — 2,350 pounds.

“We filled 94 five-gallon buckets,” Crawford said. “It was layered 7 inches thick.”

Crawford said the gum wall isn’t marketed or advertised, but it’s in all the guidebooks and tourist websites. Tours come through the alley daily.

The wall is cleaned annually, but the gum just keeps coming at an ever increasing rate. In only five months, nearly every square inch had been covered.

“It’s so colorful,” exclaimed Mari Berber of Merced, Calif. She was visiting the gum wall with boyfriend, Julian Pulido.

Like others, they had heard about the wall on social media.

“I want to go there, I want to go the Space Needle and I want to go the market,” Berber said. “That’s about it.”

The couple were shooting video and still images and posting to Facebook and Instagram.