Tuesday morning, the New York City Landmarks Preservation Commission (LPC) announced their decision to designate Philip Johnson and John Burgee’s AT&T Building, now known as 550 Madison Avenue, as a landmark.

The designation protects the exterior of the building, including the facades of the office tower, annex, and enclosed covered passageway, and notably preserving its rose Stony Creek granite cladding and the broken pediment at its crown. Going forward, any proposed alterations to the exterior will require approval and permitting by the LPC.

The LPC will also review proposals for any interior work that requires a Department of Buildings permit, to determine whether the construction will affect the building’s exterior. (Advocates for the building were up in arms earlier this year about the demolition of the lobby, which took place in January 2018.)

The decision came after months of contentious debate from architects, preservationists, and critics following the release of Snøhetta’s proposal for a renovation of the postmodern structure.

“I am thrilled the Commission has recognized the importance of the AT&T Corporate Headquarters Building,” said Frederick Bland, vice chair of the LPC. “This is the building that established postmodernism as a legitimate architectural movement. It deserves to be preserved for future generations.”

“Today’s designation of 550 Madison as a landmark secures its rightful place among the great architectural staples of New York City,” said Manhattan council member Keith Powers. “I applaud the advocates and groups that understood the significance of this postmodern landmark and fought to ensure its preservation.”