They’re called “landmarks” for a reason — giant buildings that define a city, dot its skyline, and become monuments to human architectural achievement. Only the biggest and best buildings get official names, but sometimes those names change…and it’s hard to get anybody to call these institutions by that new moniker.

Chicago’s Sears Tower

Chicago’s Sears Tower found much more fame than your average company HQ skyscraper because at the time of its opening in 1973, it was the tallest building on the planet. Several other buildings around the world have long since claimed that title…and the now nearly-done department store chain that gave the tower its name left years ago. Sears sold the building in 1994, moved out in 1995, and gave up the naming rights in 2003. Insurance company Willis Group Holdings leased a bunch of office space in the building and got the naming rights as part of the deal. Since 2009, the Sears Tower has been the Willis Tower…but most people in Chicago still call it the Sears Tower. (Willis’ CEO jokingly suggested Windy City residents call it “Big Willy”…but that didn’t catch on either.)

John Hancock Center

Perhaps the Second City’s second-most famous skyscraper is the John Hancock Center. A sleek, shiny, modern skyscraper that opened in Chicago in 1969, its 100 stories contain offices, apartments, restaurants, an observatory, and, at one time, the headquarters of John Hancock Insurance. That company left long ago, and the building’s naming rights expired in 2013. Everyone kept calling it the John Hancock, however, and in 2018, the insurance company asked the building’s ownership group to remove all “John Hancock” signage, inside and out. The naming rights are currently available (if you’re interested and have a few million bucks laying around), but until then, the John Hancock Center’s official name is also its street address: 875 North Michigan Avenue.

Pan Am Building

Right above Grand Central Station in New York City stands the 59-story Park Avenue building still referred to as the Pan Am Building. It opened and was completed in 1963 (although not in that order) and at the time offered the most office space in a single building in the world. The glamorous airline that gave the building its name used 15 floors for its corporate headquarters, and stayed there past 1981, when Metropolitan Life Insurance bought the whole skyscraper. As Pan Am slowly went out of business over the next decade, so too did its presence in the Pan Am Building — just four stories by 1991. A year later, Pan Am went out of business, prompting Metropolitan Life to get rid of the giant “PAN AM” side on the outside of the edifice…and rename it the MetLife Building.