More than 60 architects, academics and historic preservationists sent a letter to Mayor Rahm Emanuel urging him to grant landmark status to the Prentice Women’s Hospital designed by Bertrand Goldberg. Northwestern University, which owns the Streeterville building, intends to tear it down to construct a new research facility.

The letter, signed by architects such as Jeanne Gang and Frank Gehry, underscored a report by the National Trust for Historic Preservation, which found that the building “exceeds the criteria for Chicago landmark designation.”

Mr. Goldberg, the building’s architect was a student of Ludwig Mies van der Rohe and a Chicago native. He is best known for his Marina City development in Chicago, one of the first attempts to create a self-contained mixed-use urban center.

 “The engineering significance of Prentice is far greater than Marina City,” Jonathan Fine, executive director of Preservation Chicago, told local media.

"The building is designed like a tree, with seven concrete floors cantilevering off the tower’s core like branches, hovering 45 feet above the tower’s base," Time Out Chicago reported. "This leaves the inside free of interior columns, which allowed Goldberg to avoid long hallways. Instead of being arrayed in rows, patient rooms are laid out in circular hubs centered on a nurse’s station."

Mr. Fine said this approach represents the humanist characteristics of modernism and reveals Goldberg’s desire to improve the usually terrible hospital experience.

Support for the building's preservation came from around the world, with international signees from Europe, Australia and Asia. “Chicago’s global reputation as a nurturer of bold and innovative architecture will wither if the city cannot preserve its most important achievements,” the letter stated.