Final answer:
Historical advances in construction and technology, like the invention of the electric elevator and the use of steel columns, contributed to the creation of iconic skyscrapers such as the Empire State Building, Willis Tower, and Canadian National Tower, each being the tallest in the world during their respective eras.
Step-by-step explanation:
The Empire State Building, the Willis Tower (formerly called the Sears Tower), and the Canadian National Tower are significant because they each held the title of the world's tallest structure when they were built. The use of steel columns in skyscraper construction allowed buildings to reach new heights, creating stronger and lighter structures, as observed in the Willis Tower.
The progress in building such monumental structures also depended on other technological advances like the electric elevator, which further fueled the race for constructing the tallest buildings in the early 20th century.
The Home Insurance Building in Chicago, completed in 1884, is often cited as the first modern skyscraper, thanks to its steel-frame construction.
Over time, innovations in engineering and design, along with the growing value of city center real estate, led to the creation of iconic skyscrapers such as the Home Insurance Building, the Woolworth Building, and eventually, contemporary giants like the One World Trade Center, which stands as the tallest skyscraper in the United States with a symbolic height of 1,776 feet, reflecting the year the Declaration of Independence was signed.