No longer the Sears Tower - but will the new name catch on?
The Sears Tower in Chicago - one of the most famous skyscrapers in the world - is being renamed.
The 110-storey structure, which opened in 1973, is being rechristened the Willis Tower on Thursday.
London-based insurance brokerage Willis Group Holdings has secured the naming rights as part of an agreement to lease space.
But the name change has angered some protesters, who have launched a website called www.itsthesearstower.com.
Tourists from around the world have visited the tower's gallery to see views of Chicago.
Chicago teacher Marianne Turk, 46, told the Associated Press news agency that she was firmly against the change, as she waited to go up.
"It's always going to be the Sears Tower. It's part of Chicago and I won't call it Willis Tower. In Chicago we hold fast," she said.
The Willis Tower will be introduced to Chicago by the city's mayor, Richard Daley, during a public renaming ceremony hosted by Willis Group Holdings.
The company is hopeful that the name change will catch on.
"Everybody knows that tower," chief executive Joe Plumeri said ahead of the ceremony.
"If we're good corporate citizens and do what we should, hopefully Willis and the tower and Chicago will all become synonymous."
The glass cube that juts out from the viewing gallery on the 103rd floor
Other well-known buildings have undergone name changes - New York City's Pan Am Building became the MetLife Building, and Chicago's Standard Oil Building is now the Aon Center.
But people have not always taken to them.
Public relations experts said it could take decades for the new name of the Chicago skyscraper to take its place in the public consciousness.
"The Sears Tower is not just a Chicago landmark, it's a national landmark that's known around the world," Aaron Perlut, a managing partner at St Louis-based PR agency Elasticity, told Reuters news agency.
"We see it on our TVs, in movies and magazines, so it is part of pop culture."
"Gaining public acceptance of renaming the Sears Tower will be extremely challenging. Even with a very long, integrated marketing campaign we could be looking at a 20-to-30-year period," he said.
The building's original tenant, Sears Roebuck and Co, moved out in 1992 but its sign stayed on.
A real estate investment group, American Landmark Properties of Skokie, Illinois, now owns the building.