Major expansion in 1932 added a total of nine floors for more than 60 acres (24 ha), or 2.5 million square feet (230,000 m²), of floorspace.

[3] (Montgomery Ward, which became the largest retailer in the United States in the late 1930s, was eventually passed by Sears, and then was purchased and merged.)

In 1966, the Main Chicago Post Office came to a halt when a logjam of 10 million pieces of mail clogged the system for nearly a week.

[4] With Chicago rated worst in postal deliveries, a new Main Post Office to be located right across Harrison Street was proposed.

[5] A February 2006 report by the General Accounting Office stated, that it cost the government $2 million a year to maintain the retired building.

Held on August 27 and conducted by Rick Levin & Associates Inc., the auction raised $40 million, which was well over the opening bid of $300,000.

[21][22] On June 18, 2014, Bill Davies announced the formation of a $500 million joint venture with Sterling Bay Companies for phase I of the redevelopment.

[26] After sitting vacant for nearly two decades, the building was bought in 2014 by English real estate developer Bill Davies for $24 million at auction.

[28] In February 2016, Chicago mayor Rahm Emanuel pressed for development of the site, threatening to take possession of the building by use of eminent domain.

In March, the city's Department of Planning and Development issued an RFP seeking bids due June 10 for redevelopment of the site.

[38] As of 2022[update] other tenants include:[38] The building was used in the filming of Batman Begins in 2004[citation needed], and The Dark Knight in April 2007.

In the summer of 2010, Paramount Pictures and Michael Bay filmed numerous scenes for Transformers: Dark of the Moon in and around Chicago.

The old Chicago Post Office's east facade was decorated as the "Department of Health and Human Services" where the Autobots were kept by the federal government in the movies.