What was the tallest building in Chicago in 1955?

In 1955, the tallest building in Chicago was the Aon Center, originally known as the Standard Oil Building. Completed in 1930, it stands at 1,000 feet (305 meters) tall and has 83 floors. The building remained the tallest in Chicago until the completion of the Willis Tower (formerly known as the Sears Tower) in 1973.