SEATTLE — After 20 years of people sticking their gum to the walls of an alley by Seattle’s Pike Place Market, officials say it is time for a cleanup.

Pike Place Market announced this week it will take down the estimated 1 million pieces of gum off the walls of Post Alley. Known as the “gum wall,” the sticky landmark has become a popular attraction to visitors and locals.

Besides gum, people leave pictures, business cards and other mementos. Some pieces of gum were shaped into hearts and messages.

Tourist Katri Mattsson said the gum wall was “pretty gross,” but also “in way very impressive.”

The market has hired a contractor that will use steam to melt off the gum, beginning Nov. 10. Pressure washing damages the historic building too much.