The Sydney Harbour Bridge is distinctive because of its monumental granite pylons. This provided work for a large number of people near Moruya, a small farming town sitting on a great seam of granite on the South Coast of New South Wales. The quarry near the town was in operation for six years between 1925 and 1931. Three steamers, each of 300 tonnes, were specially built to transport the output of the quarry to Sydney.

In Sydney, the first tangible signs of activity indicating that bridge construction had started appeared in early 1925. A massive clearance on either side of the harbour made way for the foundations and the extensive approaches. The unseen work had gone on largely at Milsons Point where they had built two large fabricating shops. They were 500 feet long and up to 150 feet wide – huge by any standards. And they had to be for the fabrication of the steel sections and to house the confusion of heavy machinery needed for the task ahead. At full strength, 800 men were employed in the shops in three continuous shifts. Never before had Australia experienced such industrial activity.

The entire weight of the steel span was to rest on massive bearings, two on each side of the harbour. The foundations for these were a mass of concrete, 40 feet deep, embedded in solid sandstone. The men on the site were among the highest paid in the Australian workforce and the jobs were keenly sought. By May 1928, Dorman Long started constructing the first of two creeper cranes, the largest ever built. They were necessary to build the arch. And within a year, the people of Sydney could begin to get an idea of what sort of structure would become a permanent part of their skyline.

Sydney’s much larger rainbow arch – or ‘Coathanger’, as it would be known – would reach from either side of the harbour with the growing steelwork placed into position by the two creeper cranes on top. This could only be done by supporting the ever-increasing weight in some way until the two halves met in the middle and became self-supporting. As the steelwork could not be held up from below, it was decided to tie it back by steel cables anchored into rock tunnels on either side.

It was becoming more and more apparent day by day how the 38,000 tonnes of steel in the arch and the 6 million rivets were being used. Whether cooking rivets in vats of boiling oil or ramming them into position high in the sky, it was a job that called for the utmost precision and care. The safety measures were stringent in that age before hard hats. But there were the inevitable accidents.

Sydneysiders began to experience a surge of wonderment and pride as the two sections of the arch extended towards each other. It was a tense moment when the two sections of the arch, now dwarfing the buildings in Circular Quay, were about to be joined. The anchorage cables had to be delicately slackened and the two halves gently eased together and secured by massive guiding pins. The whole process occupied two weeks, as each day the rise in temperature expanded the steelwork and then it contracted during the night as temperatures fell. The lower cord was secured in August 1930.

With a speed that seems amazing even by the standards of today’s technology, the deck structure was completed by February 1931 and the long-awaited connection made between the two sides of the harbour. But before being opened, it was given some exacting tests to simulate the worst possible load conditions. Dozens of locomotives and tenders converged on all four tracks over the centre of the arch and stress measurements were taken to prove that the bridge was in fine shape and not at all likely to fall down.