Hoover Dam is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the U.S. states of Nevada and Arizona. It was constructed between 1931 and 1936 during the Great Depression and was dedicated on September 30, 1935, by President Franklin D. Roosevelt. Its construction was the result of a massive effort involving thousands of workers, and cost over one hundred lives. It was referred to as Hoover Dam after President Herbert Hoover in bills passed by Congress during its construction, but was named Boulder Dam by the Roosevelt administration. The Hoover Dam name was restored by Congress in 1947. Since about 1900, the Black Canyon and nearby Boulder Canyon had been investigated for their potential to support a dam that would control floods, provide irrigation water and produce hydroelectric power.
As the United States developed the Southwest, the Colorado River was seen as a potential source of irrigation water. An initial attempt at diverting the river for irrigation purposes occurred in the late 1890s, when land speculator William Beatty built the Alamo Canal just north of the Mexican border; the canal dipped into Mexico before running to a desolate area Beatty named the Imperial Valley.[7] Though water from the Imperial Canal allowed for the widespread settlement of the valley, the canal proved expensive to operate. After a catastrophic breach that caused the Colorado River to fill the Salton Sea,[8] the Southern Pacific Railroad spent $3 million in 1906–07 to stabilize the waterway, an amount it hoped in vain would be reimbursed by the federal government. Even after the waterway was stabilized, it proved unsatisfactory because of constant disputes with landowners on the Mexican side of the border.[9]
The Sydney Harbour Bridge is an Australian heritage-listed steel through arch bridge across Sydney Harbour that carries rail, vehicular, bicycle, and pedestrian traffic between the Sydney central business district (CBD) and the North Shore. The view of the bridge, the harbour, and the nearby Sydney Opera House is widely regarded as an iconic image of Sydney, and of Australia itself. The bridge is nicknamed "The Coathanger" because of its arch-based design.[1][2]
There had been plans to build a bridge as early as 1815, when convict and noted architect Francis Greenway reputedly proposed to Governor Lachlan Macquarie that a bridge be built from the northern to the southern shore of the harbour.[6][32] In 1825, Greenway wrote a letter to the then "The Australian" newspaper stating that such a bridge would "give an idea of strength and magnificence that would reflect credit and glory on the colony and the Mother Country".[32] Nothing came of Greenway's suggestions, but the idea remained alive, and many further suggestions were made during the nineteenth century. In 1840, naval architect Robert Brindley proposed that a floating bridge be built. Engineer Peter Henderson produced one of the earliest known drawings of a bridge across the harbour around 1857. A suggestion for a truss bridge was made in 1879, and in 1880 a high-level bridge estimated at £850,000 was proposed.[32]
