Sears Tower, the tallest tower in the Western Hemisphere at 1,725 ft and popular icon of Chicago, is to be renamed as Willis Tower as part of a rental agreement with London-based insurance company Willis Group Holdings.

The company are to consolidate five area offices and move nearly 500 Associates into Willis Tower, initially occupying more than 140,000 sq ft on multiple floors.

"Having our name associated with Chicago’s most iconic structure underscores our commitment to this great city, and recognizes Chicago’s importance as a major financial hub and international business center,” said Joseph J. Plumeri, Chairman and Chief Executive Officer, Willis Group Holdings.

The majority of Willis HRH Associates moving to Willis Tower work in the company’s retail brokerage business, which is supported by Willis’ key specialist capabilities in such areas as construction, executive risk, healthcare, property, real estate and employee benefits.

The 110 storey tower, designed by Skidmore Owings and Merrill and completed in 1973, held the record for the world’s tallest building for 25 years until the Petronas Towers in Kuala Lampur, Malaysia were built in 1998