Standing alongside the Sydney Opera House, the Sydney Harbour Bridge is prominently displayed in most postcard shots of Australia's largest city. Affectionately nicknamed "The Coathanger" for its steel through arch design, the impressive piece of engineering is the tallest of its kind in the world, measuring 134 metres above the water. It also has a rich history behind it, with plans for the bridge dating back as early as 1815, when noted architect Francis Greenway tabled a proposal to link the northern and southern shores of the harbour. 

Construction of the Sydney Harbour Bridge, image via State Library of New South Wales

While Greenway's idea was mostly disregarded, it gave licence to other architects to come forward with plans of their own. Among them were concepts for a floating bridge, a truss bridge, and a high-level bridge. More formal submissions were made when an international design competition was launched in 1900, yielding well-received schemes for a suspension bridge and steel cantilever bridge. An economic slump and a change in government would eventually stall plans for the project, though concepts were still being developed, including an unconventional three-span bridge proposed by Ernest Stowe in 1922.

Construction of the bridge in 1930, image via Royal Australian Historical Society

Plans were resuscitated following the First World War, when John Bradfield, the chief engineer appointed to the project, prepared a general design with the New South Wales Department of Public Works. Their vision for a single-arch bridge — cheaper and more rigid than the alternative cantilever and suspension bridge proposals — carried strikingly similar attributes as New York City's Hell Gate Bridge. In 1924, after a worldwide tendering process, a construction contract was awarded to Dorman Long and Co Ltd, of Middlesbrough, England. Construction would begin later that year, facilitating a road configuration that would consist of six lanes of traffic flanked by two railway tracks and a footpath. 

Sydney Harbour Bridge from Luna Park, image by Flickr user stylastles via Creative Commons

Controversially, the project required the demolition of an estimated 469 residential and commercial buildings on the north shore, with little to no compensation offered for the losses. By September 1926, the concrete piers to support the approach spans were installed on both sides of the harbour. The construction of the arch began on October 26, 1928, and its two halves touched for the first time on August 19, 1930. A day later, the milestone was celebrated in patriotic fashion by flying the Australian and United Kingdom flags from the creeper cranes.

Sydney Harbour Bridge by Night, image by Flickr user Michael Yuen via Creative Commons

Once the arch was complete, the deck itself began assembly, finishing in June 1931. The road, rails, and utility lines were then all laid that same year. First testing of the bridge began in January 1932, followed by strength load testing one month later, an exercise that saw as many as 96 steam locomotives sprawling across the bridge. Following three weeks of testing, the bridge was declared safe and ready for use. Six million rivets were fastened, 53,000 tonnes of steel used, and 1,400 workers toiled away — 16 of whom sadly died — and the bridge officially opened on March 19, 1932.

Tram services were removed from the bridge in 1958 and replaced by two additional road lanes, while 30 years later, a tunnel would be constructed to accommodate a surge in traffic. Today, the bridge carries rail, vehicular, bicycle, and pedestrian traffic, while way up top, daredevils traverse the arch as part of the famous BridgeClimb attraction.

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