The bridge was designed and built by Dorman Long and Co Ltd, Middlesbrough Teesside and Cleveland Bridge, Darlington, County Durham and opened in 1932. Until 1967 it was the city's tallest structure. According to Guinness World Records, it is the world's widest long-span bridge and it is the tallest steel arch bridge, measuring 134 metres (440 ft) from top to water level. It is also the fifth-longest spanning-arch bridge in the world.
The southern (CBD) bridge end is located at Millers Point in The Rocks area, and the northern end at Milsons Point in the lower North Shore area. It carries six lanes of road traffic on its main roadway, two lanes of road traffic (formerly two tram tracks) and a footpath on its eastern side, and two railway tracks and a bicycle path along its western side, being 305 mm (12 in) broader than the east side.
The main roadway across the bridge is known as Bradfield Highway, Sydney, and is about 2.4 kilometres (1.5 mi) long, making it one of the shortest highways in Australia. (The shortest, also called the Bradfield Highway, is found on the Story Bridge in Brisbane).
The Sydney Harbour Bridge is not completely stationary. It can rise or fall up to 18 cm (7.1 in) depending on whether it is hot or cold because the steel expands or contracts.
The arch is composed of two 28-panel arch trusses; their heights vary from 18 m (59 ft) at the centre of the arch to 57 m (187 ft) at the ends next to the pylons.
The arch has a span of 503 m and its summit is 134 m (440 ft) above mean sea level; however, expansion of the steel structure on hot days can increase the height of the arch by as much as 18 cm (7.1 in). Large steel pins support each end of the arch, allowing it to rotate to accommodate expansion and contraction caused by changes of temperature and avoiding stresses that would otherwise cause damage.
The total weight of the bridge is 39,006 tonnes (38,390 long tons). About 79% of the steel came from Middlesbrough, in the northeast of England; the rest was Australian-made. The bridge is held together by six million hand-driven rivets that were made at the Park Bridge Ironworks in Lancashire, England. 
At each end of the arch stand a pair of 89 m (292 ft) high concrete and granite pylons. The pylons were designed by the Scottish architect Thomas S. Tait a partner in the architects' firm John Burnet & Partners. The granite was quarried at Moruya, New South Wales, 314 kilometres (195 mi) south of Sydney. The concrete used was also Australian-made. Abutments, that are essential to support the loads from the arch and hold its span firmly in place, also provide a base for the pylons.
The pylons have no structural purpose; they are there to provide a frame for the arch panels and give better visual balance to the bridge. The panels were not part of the original design and were added to allay public concern about structural integrity of the bridge.
Although originally added to the bridge for their aesthetic value, all four pylons have now been put to use: the southeastern pylon contains a museum and tourist centre with a lookout of the harbour; the southwestern pylon is used by the New South Wales Roads and Traffic Authority (RTA) to support its CCTV cameras overlooking the bridge and the roads around that area; the two pylons on the north shore are venting chimneys for fumes from the Sydney Harbour Tunnel; the base of the southern pylon contains the RTA maintenance shed for the bridge, and the base of the northern pylon contains the traffic management shed for tow trucks and safety vehicles used on the bridge.
On New Year's Eve, the numbers for the countdown appear on the pylons of the bridge.
There had been plans to build a bridge as early as 1815, when Francis Greenway proposed that a bridge be built across the harbour. Nothing came of this. By 1900, a competition was launched to find a suitable design. There were many entries, but none was accepted owing to low standards.
Designs and proposals were requested in 1900, but a formal proposal was not accepted until 1911. In 1912, John Bradfield, was appointed chief engineer of the bridge project, which also had to include a railway. After travelling extensively to look at a number of bridges worldwide, he based his idea upon New York City's Hell Gate Bridge. Bradfield completed a formal design for a single-arch bridge in 1916, but plans to implement the design were postponed until 1922, primarily because of World War I. 
Serious initiatives started after the end of World War I. In November 1922 the New South Wales parliament passed laws that allowed the bridge's construction. Construction tenders for the bridge were requested the same year. Either an arch or a cantilever bridge would meet the requirements. Dr J. J. C. Bradfield was responsible for setting the parameters of the tendering process. The British firm Dorman Long and Co Ltd, of Middlesbrough, won. To offset concerns about a foreign firm participating in the project, assurances were given by Bradfield that the workforce building the bridge would all be Australians. Dorman Long and Co's Consulting Engineer, Sir Ralph Freeman, carried out the detailed design of the bridge. Bradfield and his staff were to ultimately oversee the entire bridge design and building process. Architects for the contractors was the British firm John Burnet & Partners of Glasgow, Scotland.
The building of the bridge coincided with the construction of a system of underground railways in Sydney's CBD, known today as the City Circle, and the bridge was designed with this in mind. The bridge was designed to carry six lanes of road traffic, flanked by two railway tracks and a footpath on each side. Both sets of rail tracks were linked into the underground Wynyard railway station, on the south side of the bridge, by symmetrical ramps and tunnels. The eastern-side railway tracks were intended for use by a planned rail link to the Northern Beaches; in the interim they were to be used to carry trams from the North Shore into a terminal within Wynyard station.
The Bradfield Highway, which is the paved section of the bridge and its approaches, and is the shortest highway in Australia, still bears Bradfield's name to this day.
In 1923, 799 homes and a high school campus were demolished in preparation for construction. The owners of these homes received compensation, but their occupants did not. 
The building of the bridge was under the management of Bradfield. Three other people were involved in the bridge's design and construction: Lawrence Ennis, the engineer-in-charge at Dorman Long and Co was the main supervisor (Bradfield visited occasionally throughout the project and, in particular, at the many key stages of the project, to inspect progress and make managerial decisions); Edward Judge was chief technical engineer of Dorman Long and later became president of the British Iron and Steel Federation; Sir Ralph Freeman was hired by the company to design the accepted model in further detail. Later a bitter disagreement broke out between Bradfield and Freeman as to who actually designed the bridge. Another name connected with the bridge's design is that of Arthur Plunkett.
The official ceremony to mark the "turning of the first sod" occurred on 28 July 1923. This was followed by the building of two worksheds at Milsons Point to assist in building the bridge—the light and heavy workshops. Their purpose was to build the bridge's many parts.
In January 1925, the excavations to build the abutments and approach spans began. In October 1925, the building of the abutments and approach spans themselves began, and these were completed in September 1928. Construction of the bridge itself began in December 1928, with the construction of the bridge parts in the workshops.
Construction of the arch of the bridge began in 1929, with two separate teams building the arch on each side using creeper cranes. The first panel was erected on the southern side in March 1929. The southern end of the bridge was worked on a month ahead of the northern end, in order to detect any errors and to ensure that they did not happen on the northern side.
During construction, the two halves of the arch were held up by numerous support cables. Once the arch halves were completed the cables were slowly released to bring the two halves of the arch together. This was finished on the afternoon of 19 August 1930. Ennis and four associates personally witnessed this whilst standing on top of the bridge. Following a parting due to the contraction of metal in the evening, the ends were rejoined at 10 pm, and have remained joined since then. The support cables were then surplus to the design and removed. They were subsequently used as support cables for the Walter Taylor Bridge, over the Brisbane River in the western suburbs of Brisbane, Queensland. sails under the completed arch from which the deck is being suspended.]] The road and the two sets of tram and railway tracks were completed in 1931. Power and telephone lines, and water, gas and drainage pipes were also all added to the bridge in that year. On 19 January 1932, the first test train, a steam locomotive, safely crossed the bridge. About 90 others also crossed the bridge in the months that followed as part of a series of tests to ensure the bridge's safety.
The construction worksheds were demolished after the bridge was completed, and the land that they were on is now occupied by Luna Park.
The standards of industrial safety during construction were poor by today's standards. Sixteen workers died during construction, but surprisingly only two from falling off the bridge. Several more were injured from unsafe working practices undertaken whilst heating and inserting its rivets, and deafness experienced by many of the workers in later years was blamed on the project. Henri Mallard between 1930 and 1932 produced hundreds of stills and film footage. which reveal at close quarters the bravery of the workers in tough Depression-era conditions.
The total financial cost of the bridge was $10 million (double the original quote). This was not paid off in full until 1988.
declares the bridge open]]
The bridge was formally opened on 19 March 1932. Amongst those who attended and gave speeches were the state Governor, Sir Philip Game, the Minister for Public Works, and Ennis. The Labor Premier of New South Wales, Jack Lang, was to open the bridge by cutting a ribbon at its southern end.
However, just as he was about to do so, a man in military uniform rode in on a horse, cutting the ribbon and opening the Sydney Harbour Bridge in the name of the people of Australia before the official ceremony began. He was promptly arrested. The ribbon was hurriedly retied and Lang performed the official opening ceremony. After he did so, there was a 21-gun salute and an RAAF flypast. The intruder was identified as Francis de Groot. He was convicted of offensive behaviour and fined £5 after a psychiatric test proved he was sane. He was a member of a right-wing paramilitary group called the New Guard, opposed to Lang's leftist policies and resentful of the fact that King George V had not been asked to open the bridge. De Groot was not a member of the regular army but his uniform allowed him to blend in with the real cavalry. This incident was one of several involving Lang and the New Guard during that year.
A similar ribbon-cutting ceremony on the bridge's northern side by North Sydney's mayor, Alderman Primrose, was carried out without incident. It was later discovered that Primrose was also a New Guard member but his role in and knowledge of the de Groot incident, if any, are unclear.
A message from a primary school in Tottenham, 515 km (320 mi) away in rural New South Wales, arrived at the bridge on the day and was presented at the opening ceremony. It had been carried all the way from Tottenham to the bridge by relays of school children, with the final relay being run by two children from the nearby Fort Street Boys' and Girls' schools. Other features of the opening ceremony included a vast display of floats and marching bands — one quite remarkable by Depression standards. The public was allowed to walk on the highway. There had been numerous preparatory arrangements. On 14 March 1932, three postage stamps were issued to commemorate the imminent opening of the bridge. One of these stamps, with a face value of five shillings, is worth several hundred dollars today.  Several songs were also composed in advance for the occasion. These have now been largely lost or forgotten.
The bridge itself was regarded as a triumph over Depression times, earning the nickname "the Iron Lung", as it kept many Depression-era workers employed.
From the Sydney CBD side, motor vehicle access to the bridge is normally via Grosvenor Street, Clarence Street, Kent Street, the Cahill Expressway, or the Western Distributor. Drivers on the northern side will find themselves on the Warringah Freeway, though it is easy to turn off the freeway to drive westwards into North Sydney or eastwards to Neutral Bay and beyond upon arrival on the northern side.
The bridge originally only had four wider traffic lanes occupying the central space which now has six, as photos taken soon after the opening clearly show. The width of the lanes now is so small that buses passing each other in adjacent lanes do so a few inches apart.
In 1958, tram services across the bridge were withdrawn and the tracks replaced by two extra road lanes; these lanes are now the leftmost southbound lanes on the bridge and are still clearly distinguishable from the other six road lanes. Lanes 7 and 8 now connect the bridge to the elevated Cahill Expressway that carries traffic to the Eastern Distributor.
In 1988, work began to build a tunnel to complement the bridge. It was determined that the bridge could no longer support the increased traffic flow of the 1980s. The Sydney Harbour Tunnel was completed in August 1992. It is intended for use only by motor vehicles. Before it was officially opened for use, the tunnel was made open for pedestrian access, with people on that day able to walk down the tunnel's roadway.
The Bradfield Highway is designated as a Travelling Stock Route which means that it is permissible to herd livestock across the bridge, but between midnight and dawn, and after giving notice of intention to do so. In practice, owing to the high-density urban nature of modern Sydney, and the relocation of abattoirs and markets, such an event has not taken place for approximately half a century.
The bridge is equipped for tidal flow operation, permitting the direction of traffic flow on the bridge to be altered to better suit the morning and evening rush hours' traffic patterns.
The bridge has eight lanes in total, numbered one through eight from west to east. Lanes three, four and five are reversible. One and two always flow north. Six, seven and eight always flow south. The default is four each way. For the morning rush hour, the lane changes on the bridge also require changes to the Warringah Freeway, with its inner western reversible carriageway directing traffic to the bridge lane numbers three and four southbound.
The bridge has a series of overhead gantries which indicate the direction of flow for each traffic lane. A green arrow pointing down to a traffic lane means the lane is open. A flashing red 'X' indicates the lane is closing, but is not yet in use for traffic travelling in the other direction. A static red 'X' means the lane is in use for oncoming traffic. This arrangement was introduced in the 1990s, replacing a slow operation where lane markers were manually moved to mark the centre median.
It is possible to see odd arrangements of flow during night periods when maintenance occurs, which may involve completely closing some lanes. Normally this is done between midnight and dawn, because of the enormous traffic demands placed on the bridge outside these hours.
As of 27 January 2009 there is a variable tolling system for all vehicles headed into the CBD (southbound). The toll paid is dependent on the time of day in which the vehicle passes through the toll plaza. The toll varies from a minimum value of $2.50 to a maximum value of $4. There is no toll for northbound traffic (though taxis travelling north may charge passengers the toll in anticipation of the toll the taxi must pay on the return journey). There are toll plazas at the northern and southern ends. The two eastern lanes (which continue over the Cahill Expressway at the southern end of the bridge) have their tollbooths at the northern end, while the other southbound lanes (for CBD traffic) are serviced by tollbooths at the southern end of the bridge. There is a bridge-long median strip between lanes 6 and 7 to separate traffic which has already paid the toll (at the northern end) from other southbound traffic (which must pay the toll at the southern end).
The toll was originally placed on travel across the bridge, in both directions, to recoup the cost of its construction. This cost was recovered in the 1980s, but the toll has been kept (indeed increased) by the state government's Roads and Traffic Authority to recoup the costs of the Sydney Harbour Tunnel.
After the decision to build the Sydney Harbour Tunnel was made in the early 1980s, the toll was increased (from 20 cents to $1, then to $1.50, and finally to $2 by the time the tunnel opened) to pay for its construction. The tunnel also had an initial toll of $2 southbound. After the increase to $1, the concrete barrier on the bridge separating the Bradfield Highway from the Cahill Expressway was increased in height, because of the large numbers of drivers crossing it illegally from lane 6 to 7, in order to avoid the toll. The toll for all southbound vehicles was increased to $3 in March 2004.
Originally it cost a car or motorcycle six pence to cross, a horse and rider being three pence. Use of the bridge by bicycle riders (provided that they use the cycleway) and by pedestrians is free. Later governments capped the fee for motorcycles at one-quarter of the passenger-vehicle cost, but now it is again the same as the cost for a passenger vehicle.
In July 2008, a new electronic tolling system called E-Tag was introduced. The Sydney Harbour Tunnel was converted to this new tolling system while the Sydney Harbour Bridge itself had several cash lanes. The electronic system as of 12 January 2009 has now replaced all booths with E-tag lanes..
Pedestrian access from the northern side involves climbing an easily-spotted flight of stairs at Milsons Point. Pedestrian access on the southern side is more complicated, but signposts in the Rocks area now direct pedestrians to the long and sheltered flight of stairs that leads to the bridge's southern end. These stairs are located near Gloucester Street and Cumberland Street.
The bridge can also be accessed from the south by getting on Cahill Walk, which runs along the Cahill Expressway. Pedestrians can access this walkway from Circular Quay by a flight of stairs or a lift. Alternatively it can be accessed from the Botanic Gardens.
The bridge lies between Milsons Point and Wynyard railway stations, located on the north and south shores respectively, with two train lines running along the western side of the bridge. Milson's Point station is part of the North Shore line.
In 1958, tram services across the bridge were withdrawn and the tracks they had used were removed and replaced by two extra road lanes; these lanes are now the leftmost southbound lanes on the bridge and are still clearly distinguishable from the other six road lanes. The original ramp that took the trams into their terminus in the underground Wynyard railway station is still visible at the southern end of the main walkway under lanes 7 and 8 although the tunnels have been sealed off.
In 2006, the first complete repainting for many years commenced. A reason for the decision was the concern that weight of the many layers of paint acquired over the years might be having a destructive effect on the bridge's structure. Because of the previous regime of continuous maintenance painting with lead-based paint, precautions had to be taken to prevent falling paint from contaminating the harbour. This required that each section being painted be sealed off and blasted to remove old paint which was then extracted by vacuum.
The southeast pylon served for many years as a lookout and tourist attraction for Sydney, containing a number of telescopes and antiquated arcade games which operated on pennies, long after that currency had gone out of circulation. The couple that ran this tourist venue also kept a number of white cats which gave the interior of the pylon a memorable odour. The pylon has recently been renovated and returned to its tourist function.
Since 1998, BridgeClimb has made it possible for tourists to climb the southern half of the bridge. Tours run throughout the day, from dawn to dusk, and are only cancelled for electrical storms or high wind. Night climbs are also available. Groups of climbers are provided with protective clothing appropriate to the prevailing weather conditions and are given an orientation briefing before climbing. During the climb, attendees are secured to the bridge by a wire lifeline. Each climb begins on the eastern side of the bridge and ascends to the top. At the summit, the group crosses to the western side of the arch for the descent. Each climb is a three-and-a-half-hour experience.
In December 2006, BridgeClimb launched an alternative to climbing the upper arches of the bridge. The Discovery Climb allows climbers to ascend the lower chord of the bridge and view its internal structure. From the apex of the lower chord, climbers ascend a staircase to a platform at the summit.
BridgeClimb celebrated its 10th anniversary on 1 October 2008, and is investigating the possibilities of other 'bridge climbs' around the world. Negotiations are currently underway for a similar operation on the Brooklyn Bridge in New York City.
Since the opening, the bridge has been the focal point of much tourism and national pride. In 1982, the bridge celebrated the 50th anniversary of its opening. Once again, the bridge was closed to vehicles and pedestrians allowed full access for the day. The celebrations were attended by Edward Judge, who represented Dorman Long.
Australia's bicentennial celebrations on 26 January 1988 attracted large crowds in the bridge's vicinity as merrymakers flocked to the foreshores in order to view the events on the harbour. The highlight was the biggest parade of sail ever held in Sydney, with square-riggers from all over the world, surrounded by hundreds of smaller craft of every description, passing majestically under the Sydney Harbour Bridge. The day's festivities culminated in a fireworks display in which the bridge was the focal point of the finale, with fireworks streaming from the arch and roadway. This was to become the pattern for later firework displays.
During the millennium celebrations in 2000, the Sydney Harbour Bridge was lit up with the word "Eternity", as a tribute to the legacy of Arthur Stace a Sydney artist who for many years inscribed that word on pavements in chalk in beautiful copperplate writing despite the fact that he was illiterate.
In May 2000 the bridge was closed to vehicular access for a day to allow a special reconciliation march—the "Walk for Reconciliation"—to take place. This was part of a response to an Aboriginal Stolen Generations inquiry, which found widespread suffering had taken place amongst Australian Aboriginal children forcibly placed into the care of white parents in a little-publicised state government scheme. Around a million Australians walked the bridge in a symbolic gesture of crossing a divide.
During the Sydney 2000 Olympics in September and October 2000, the bridge was adorned with the Olympic Rings. It was included in the Olympic torch's route to the Olympic stadium. The men's and women's Olympic marathon events likewise included the bridge as part of their route to the Olympic stadium. A fireworks display at the end of the closing ceremony ended at the bridge. The east-facing side of the bridge has been used several times since as a framework from which to hang static fireworks, especially during the elaborate New Year's Eve displays.
In 2005 Mark Webber drove a Williams-BMW Formula One car across the bridge.
On 25 October 2009 the premier of NSW Nathan Rees laid turf across the bitumen on the bridge. 6000 people were invited to have a picnic. There has been speculative due to the success of this event, that it could be an annual event.
In 2007, the 75th anniversary of its opening was commemorated with an exhibition at the Museum of Sydney, called "Bridging Sydney" . An initiative of the Historic Houses Trust, the exhibition featured dramatic photographs and paintings with rare and previously unseen alternative bridge and tunnel proposals, plans and sketches.
On 18 March 2007, the Sydney Harbour Bridge celebrated its 75th anniversary. The occasion was marked with a ribbon-cutting ceremony by the governor, Marie Bashir and the premier of New South Wales, Morris Iemma. The bridge was subsequently open to the public to walk southward from Milsons Point or North Sydney. Several major roads, mainly in the CBD, were closed for the day. An Aboriginal smoking ceremony was held at 7pm.
Approximately 250,000 people (50,000 more than were registered) took part in the event. Bright yellow souvenir caps were distributed to walkers. A series of speakers placed at intervals along the bridge formed a sound installation. Each group of speakers broadcast sound and music from a particular era (eg King Edward VIII's abdication speech; Gough Whitlam's speech at Parliament House in 1975), the overall effect being that the soundscape would "flow" through history as walkers proceeded along the bridge. A light-show began after sunset and continued late into the night, the bridge being bathed in constantly changing, multi-coloured lighting, designed to highlight structural features of the bridge. In the evening the bright green caps were replaced by orange caps with a small, bright LED attached. The bridge was closed to walkers at about 8.30 p.m.
New Year Eve
As part of the fireworks display on New Year's Eve the Sydney Harbour Bridge has a light display on a framework is used to complement the fireworks. As the scaffolding and framework are clearly visible for some weeks before the event, revealing the outline of the design, there is much speculating as to how the effect is to be realised. The effects have been as follows:
- 1998-99 - Smiley face with hair.
- 1999-2000 - "Eternity" in copperplate writing, in honour of Arthur Stace.
- 2000-01 - Rainbow Serpent and Federation Star.
- 2001-02 - Uluru
- 2002-03 - Dove of peace
- 2003-04 - Light show
- 2004-05 - Disco ball
- 2005-06 - Love heart (Three concentric love hearts with lights behind the middle.)
- 2006-07 - Coathanger and a diamond to celebrate the bridge's 75th anniversary or Diamond Jubilee in 2007.
- 2007-08 - Hourglass
- 2008-09 - Sun
- 2009-10 - Yin and yang
on the North Shore|thumb|left|600px]]
- Australian Landmarks
- Story Bridge, Brisbane — The other major bridge designed by John Bradfield.
- List of arch bridges by length
- Four papers on the design and construction of the bridge in volume 238 of the Minutes of Proceedings of the Institution of Civil Engineers, 1935 Kinley
- Knezevic, Daniel,(1947), 'The Lost Bridge',
- Sydney Harbour Bridge in the Structurae database
- Sydney City Council
- Sydney Harbour Bridge turns 75 - Feature from Daily Telegraph
- 75th Anniversary Celebrations
- Bridge during construction
- Air views of the opening celebrations, 19 March 1932 / photographed by W. E. Searle
- Buildings and roads around North Sydney and Sydney Harbour Bridge, 1958–1961 / Wolfgang Sievers
- Sydney Harbour Bridge during the Olympic Games, 19-26 September 2000 / Loui Seselja
- Picnic on Sydney Harbour Bridge / Sigmate Studio
- Breakfast on the Bridge / Daniel Boud