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Map shows boundaries of counties and hundreds, telegraph line and notes and routes made by the telegraph exploration and construction parties, etc in Australia's Top End. These parties were variously led by John Ross, in central and northern Australia, GG McLachlan in northern Australia, and William McMinn in central Australia.

The construction of the Overland Telegraph Line was an enormous engineering feat. It entailed stringing a strand of copper wire across the centre of the Australian continent, to link it to the underwater telegraph cable at Port Darwin. It would enable almost instant communication with the rest of the world.

When South Australia won the contract, Charles Todd as Superintendent of Telegraphs was responsible for overseeing the success of this endeavour. The route across the continent had only been pioneered in 1862 by John McDouall Stuart, and the settlement of Port Darwin established in 1866. Extensive exploration was still needed in order to select the best route for the Telegraph Line, particularly in central Australia and at the northern end of the proposed line. Here Stuart had reached the coast further to the east, at Point Stuart. Work on the line began in September 1870 and was divided into three sections: southern, central and northern. These exploration and construction parties added greatly to the knowledge of the country. The final link was made on 22 August 1872.

For many years the Overland Telegraph Line was a focal point in Australian exploration with explorers leaving from or reaching for the safety of the Line. In February 1942, during World War II, the underwater cable was cut in anticipation of an invasion. This followed the surprise Japanese air raid on Darwin.

The Overland Telegraph Line continued to function until the 1970s when it was finally replaced by the new technology of microwave links.

Todd, Charles Sir, 1826-1910

Stuart, John McDouall, 1815-1866

Ross, John, 1817-1903

McMinn, William, 1844-1884

McLachlan, George G.

The centenary of the Adelaide-Darwin overland telegraph line : papers presented to a symposium sponsored by the Institution of Engineers, Australia and the Australian Post Office Sydney: Australian Post Office, 1972

Giles, Alfred, Exploring in the 'seventies and the construction of the Overland Telegraph Line Adelaide : Friends of the State Library of South Australia, 1995

Taylor, Peter, An end to silence: the building of the Overland Telegraph Line from Adelaide to Darwin Sydney: Methuen Australia, 1980

State Library of South Australia: Mortlock Wing. Taking it to the edge August 2004-