John Hancock Tower

The John Hancock Tower, colloquially known as the Hancock, is a 60-story, 790-foot (240 m) skyscraper in the Back Bay neighborhood of downtown Boston, Massachusetts. The pinnacle height (including antennas) is 852 feet (260 m). Designed by Henry N. Cobb of the firm I. M. Pei & Partners, it was completed in 1976, and has held the title as the tallest building in New England ever since. In 2015, the lease belonging to the John Hancock Mutual Life Insurance Company, for which the skyscraper was named, expired, and it was renamed to its address at 200 Clarendon Street.

The building is widely known for its prominent structural flaws, including an analysis that the entire building could overturn under certain wind loads and a prominent design failure of its signature blue windows, which allowed any of the 500-pound (230 kg) window panes to detach and fall, up to the full height of the building, endangering pedestrians below.

The street address is 200 Clarendon Street, but occupants also use "Hancock Place" as a mailing address for offices in the building. John Hancock Insurance was the primary tenant of the building at opening, but the company announced in 2004 that some offices would relocate to a new building at 601 Congress Street, in Fort Point, Boston. The tower was originally named for the insurance company that occupied it, which in turn was named for John Hancock, a signatory of the United States Declaration of Independence.

Minimalism was the design principle behind the tower. The largest possible panes of glass were used, there are no spandrel panels, and the mullions are minimal. Cobb added a geometric modernist twist by using a parallelogram shape for the tower floor plan. From the most-common views, this design makes the corners of the tower appear very sharp. The highly-reflective window glass is tinted slightly blue, which results in the tower having only a subtle contrast with the sky on a clear day. As a final modernist touch, the short sides of the parallelogram are each marked with a deep vertical notch, breaking up the tower's mass and emphasizing its verticality. In late evening, the vertical notch to the northwest catches the last light of the sky, while the larger portions of glass reflect the darkening sky.

A major concern of the architects while designing the tower was its proximity to Boston's Trinity Church, a prominent National Historic Landmark. Their concern led them to redesign the tower's plans, as there was a public outcry when it was revealed that the Hancock Tower would cast its shadow on the church.

In 1977, the American Institute of Architects presented the firm with a National Honor Award for the building, and in 2011 conferred on it the Twenty-five Year Award.

The building was a much-anticipated landmark designed by a well-respected architect, but was known in the 1970s for its engineering flaws as well as for its architectural achievement. The opening of the building was delayed from 1971 to 1976, and the total cost is rumored to have increased from $75 million to $175 million. It was an embarrassment for the firm, for modernist architects, and for the architecture industry.

During the excavation for the tower's foundation, temporary steel retaining walls were erected to create a space in which to build. The walls warped, giving way to the clay and mud fill of the Back Bay which they were supposed to hold back. The shifting soils damaged utility lines, the sidewalk pavement, and nearby buildings—including the historic Trinity Church across St. James Avenue. Trinity Church won an $11 million lawsuit to pay for repairs.