The Cahill Expressway, which carries a railway and a roadway across the waterfront of Circular Quay, Sydney, is the first true freeway constructed in Australia and is a prime example of the growth in and development of the concrete jungles of Australia's capital cities during the Baby Boomer years. It is named after the then NSW Premier Joseph Cahill, who also approved construction of the Sydney Opera House. While being a vital link in the Sydney road system, it is generally not well loved by Sydneysiders, who dislike its ugly appearance and its division of the city from its picturesque harbour.

The Cahill Expressway in many ways embodies the concept of progress and development as it was intrepreted by town planners and developers in the post World War II years. The present concern for the consveration of the environment was of little consequence, the visual impact of a structure like the Cahill Expressway on what was the gateway to Australia was seen as irrelevant by the decision makers; the replacement of the existing with concrete and steel structures, no matter how ugly they might be, was seen as the price one had to paid for progress.

Circular Quay station. The roadway runs on the upper deck above the trains	The road deck of the Cahill Expressway above Circular Quay station

Not everyone in the 1940s shared this view, however; the idea of a freeway across the front of Circular Quay was controversial from the day the proposal was first made public in 1945. When the design was released in 1948, the protests started in ernest. The expressway was described as ‘ridiculous’, ugly’, ‘unsightly’ and a ‘monstrosity’. Sydney Morning Herald writer Elizabeth Farrelly described the freeway as 'doggedly symmetrical, profoundly deadpan, severing the city from the water on a permanent basis'.

Concerned residents of Sydney formed the Quay Planning Protest Committee to fight the proposal, but without success. To the politicians of the day, the expressway represented the vision for modern Sydney and nothing was going to stop it. The Premier J. J. Cahill described it at the opening on 24th March 1958 as ‘a striking symbol of Sydney’s growth and maturity and a monument to the skill and industry of the people’ (Sydney Morning Herald, 25th March, 1958).

Work began on the Cahill Expressway in 1955. Terraces were demolished along York Street North to make way for the new road that would run above a new elevated railway station. This stage was completed in 1955.  Work on the second stage of the expressway – which became known as the Eastern Distributor – began almost immediately. A cutting went beside Macquarie Street, swept past the Mitchell Library, between the Domain and the Botanic Gardens and down to Woolloomooloo.  Once the cutting was completed, road bridges were built over parts of the expressway.

Ever since its completion in 1958, its demolition has continued to be proposed, most prominently by former Australian Prime Minister Paul Keating, who in 1994 offered AU$150 million in federal funds toward such a project. The then NSW Premier, John Fahey, rejected the proposal however because of the cost and resultant traffic problems. In 2005, the cost of demolition was estimated at more than AU$1 billion, and the traffic problems resulting from the removal of the link would be severe, given the lack of alternate routes. However, it is not without precedent; for example, in San Francisco in 1985, the Board of Supervisors voted to demolish the elevated Embarcadero Freeway which similarly divided the city from its waterfront. It was subsequently demolished after being damaged in the 1989 earthquake.