Chicago’s Old Main Post Office Building was approved as an official City of Chicago landmark by City Council today.

Designed by Graham, Anderson, Probst & White and built in phases from 1921 to 1932, the 2.3-million-square-foot structure at 433 W. Van Buren St. is known for its critical role as the nexus of the U.S. mail system until 1996, when Post Office operations relocated to a more modern structure nearby.

Listed on the National Register of Historic Places and designed largely in the Art Deco style, the 12-story structure is clad with gray limestone accented with black granite at the ground level. The proposed designation will protect the building’s exteriors and lobby from significant alteration or demolition.

The property’s owner, 601W Cos., is implementing a $292 million rehabilitation as offices and retail space. The project will comprehensively update all interiors and exterior spaces, building systems, windows, elevators, and common areas. The work will also include repairs and improvements to existing rights-of-way for the Eisenhower Expressway and Amtrak railroad trains in the building’s lower levels. The work will be supported by Cook County’s Class L property tax incentive program, which lowers the tax rate on designated landmarks undergoing significant rehabilitation.

The landmark designation and Class L incentive were recommended by the Commission on Chicago Landmarks in October 2017.

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