What was Chicago's Willis Tower originally called?

Chicago’s Willis Tower was originally called the Sears Tower.

The skyscraper was commissioned as the headquarters of Sears, Roebuck & Company and completed in 1973. It was designed by Skidmore, Owings & Merrill, with architect Bruce Graham and structural engineer Fazlur Rahman Khan playing leading roles. Its bundled-tube structural system allowed the tower to rise efficiently while resisting wind forces.

The building was renamed Willis Tower in 2009 after insurance broker Willis Group Holdings became a major tenant. Many Chicagoans and visitors still use the original name. When completed, the Sears Tower was the world’s tallest building, taking the title from New York’s World Trade Center. It held that distinction until 1998, when Kuala Lumpur’s Petronas Towers became taller by architectural-height measures.