Hoover Dam
- Cost then: $49 million (contract awarded on March 4, 1931).
- Cost now: $703 million.
- Time to build: Five years.
- Dimensions: 726.4 feet tall, 6.6 million tons.
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- What went into it: The dam required excavating more than 5.5 million cubic yards of material and placing more than 1 million cubic yards of earth and rock fill. It contains 4.36 million cubic yards of concrete and 45 million pounds of reinforcement steel.
- Why it's significant: When it was completed in 1935, Hoover Dam was the highest dam in the world by 300 feet and is still the highest concrete dam in the Western Hemisphere, according to the American Society of Civil Engineers, which has rated the dam as one of the Seven Modern Wonders of the World.
Sources: U.S. Bureau of Reclamation, ASCE
Golden Gate Bridge
- Cost then: $35 million in 1932.
- Cost now: $557 million, though the bridge's official website says it would be about $1.2 billion in 2003 dollars because of factors such as the extent of environmental reviews and cost of labor and materials.
- Time to build: Slightly more than four years.
- Dimensions: 1.7 miles long, 90 feet wide, 746 feet tall (tower height above water), 894,500 tons
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- What went into it: The bridge contains 83,000 tons of steel and 389,000 cubic yards of concrete. More than 80,000 miles of galvanized steel wire was used just for the two main cables which pass over the tops of the two main towers.
- Why it's significant: The bridge's 4,200-foot-long suspension span was the longest in the world from the time of its construction in 1937 until New York City's Verrazano Narrows Bridge opened in November 1964. It was named one of the 10 Monuments of the Millennium by the American Society of Civil Engineers.
Sources: Golden Gate Bridge, Highway and Transportation District, ASCE
St. Lawrence Seaway
- Cost then: $470 million in 1954.
- Cost now: $3.8 billion.
- Time to build: Four years, eight months.
- Dimensions: 2,342 miles long from the Atlantic Ocean to Duluth, channel maintained at minimum depth of 27 feet.
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- What went into it: New channels were dug and existing channels were dredged to create the seaway. Construction required resettling entire communities, with about 6,500 people relocated to new homes and 550 homes moved. The related power development flooded 100 square miles. The seaway has 15 locks.
- Why it's significant: The seaway is considered one of the outstanding engineering feats of the 20th century. Since it opened to ships in 1959, the seaway has carried more than 2.75 billion tons of cargo with an estimated value of more than $375 billion.
Sources: The St. Lawrence Seaway Management Corp. and St. Lawrence Seaway Development Corp.
Empire State Building
- Cost then: $41 million in 1930 (including land cost).
- Cost now: $535 million.
- Time to build: One year, 45 days.
- Dimensions: 1,250 feet tall (1,454 feet to the top of the lightning rod), 365,000 tons
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- What went into it: The building boasts 103 floors, 6,500 windows, 73 elevators, 70 miles of water pipe, 473 miles of electrical wire and 1,060 miles of telephone cable. Its steel frame alone weighs 60,000 tons.
- Why it's significant: From the time of its completion Nov. 13, 1930, the Empire State building was the world's tallest building until the 1,368-foot-tall One World Trade Center was completed in 1972. It was built incredibly fast, with the framework rising at a rate of 4½ stories per week. The American Society of Civil Engineers designated the building as the Monument of the Millennium for civil engineering achievements in skyscrapers.
Sources: The Empire State Building Official Internet
