[9] The building is home to several offices and restaurants, as well as about 700 condominiums, and at the time of its completion contained the highest residence in the world.

The observatory (360 Chicago),[11] which competes with the Willis Tower's Skydeck, has a 360° view of the city, up to four states, and a distance of over 80 miles (130 km).

[15] The project, which would become the world's second tallest building at opening, was conceived and owned by Jerry Wolman in late 1964.

Construction of the tower was interrupted in 1967 due to a flaw in an innovative engineering method used to pour concrete in stages, that was discovered when the building was 20 stories high.

Wolman's bankruptcy resulted in John Hancock taking over the project, which retained the original design, architect, engineer, and main contractor.

[17] On December 10, 2006, the non-residential portion of the building was sold by San Francisco–based Shorenstein Properties for $385 million[a] and was purchased by a joint venture of Chicago-based Golub & Company and the Whitehall Street Real Estate Funds.

[23] In June 2013, a venture of Chicago-based real estate investment firm Hearn Co., New York–based investment firm Mount Kellett Capital Management L.P. and San Antonio–based developer Lynd Co. closed on the expected acquisition of 875 North Michigan Avenue's 856,000 square feet (79,500 m2) of office space and 710-car parking deck.

[24] Hustle up the Hancock is an annual stair climb race up the 94 floors from the Michigan Avenue level to the observation deck.

The building is home to the transmitter of Univision's WGBO-DT (channel 66), while all other full-power television stations in Chicago broadcast from Willis Tower.

The City Colleges of Chicago's WYCC (channel 20) transmitted from the building until November 2017, when it departed the air as part of the 2016 FCC spectrum auction.

Wearing a wetsuit and using a climbing device that enabled him to ascend the I-beams on the building's side, Goodwin battled repeated attempts by the Chicago Fire Department to knock him off.

[28][29] On March 9, 2002, part of a scaffold fell 43 stories after being torn loose by wind gusts around 60 mph (100 km/h) crushing several cars, killing three people in two of them.

The remaining part of the stage swung back-and-forth in the gusts repeatedly slamming against the building, damaging cladding panels, breaking windows, and sending pieces onto the street below.

This is one of the engineering techniques which the designers used to achieve a record height; the tubular system is the structure that keeps the building upright during wind and earthquake loads.

It was pioneered by Bangladeshi-American structural civil engineer Fazlur Khan and chief architect Bruce Graham.

The interior was remodeled in 1995, adding to the lobby travertine, black granite, and textured limestone surfaces.

A band of white lights at the top of the building is visible all over Chicago at night, and changes colors for different events.

[42] On its 44th floor, the building has a 5,200 square feet (480 m2) grocery store accessible only to apartment residents and office tenants.

[44] The elevators that serve the top three public floors are credited as the fastest in both North America and the Western Hemisphere.

[40] Located on the 94th floor, 360 Chicago Observation Deck is 875 North Michigan Avenue's horizon observatory.

It has been independently owned and operated since 2014 as an subsidiary of the Paris, France-based observation deck company Magnicity (formerly known as the "Montparnasse 56 Group").

[59] In September 2023, the Signature Room abruptly ceased operations, with ownership citing "severe economic hardship" that they attributed to the impact of the earlier COVID-19 pandemic.

[49] Months later, it was announced that Skidmore, Owings & Merrill (the architectural firm that designed the building in the 1970s) would be involved in re-imaging the two floors.

[55] Housed within several of the lower levels of the building is a parking garage, which cars enter and depart via a spiral vehicle ramp.

[67] In 1988, plans were unveiled by the John Hancock Mutual Life Insurance Company (the owners of the building at the time) to replace the plaza with a "$20 million[i] glass and marble three-story atrium".

This atrium proposal faced backlash from local residents who felt that such an addition would mar the appearance of the landmark building.

In 1999, Chicago Tribune architecture critic Blair Kamin wrote that this renovation had made the plaza a more "welcoming" space.

[70] In November 2012, Boston-based American Tower Corp affiliate paid $70 million[j] to acquire ownership of the antennas.