On 22 August 1872, the Overland Telegraph line between Adelaide and Darwin was finally connected. It was the result of years of planning and 23 months of arduous construction through the arid centre of the continent and  the wet, mosquito-infested terrain of the Top End. The telegraph involved 36,000 poles across 2,839 kilometres, from Port Augusta in the south to Darwin in the north, through territory virtually unexplored by Europeans. This huge logistical achievement has been called the greatest  engineering feat of the 19th-century Australia. 

The coin displays a stylised representation of telegraph poles and  their shadows, with a stylised cloudy sky. Also included in the design is the inscription ‘150TH ANNIVERSARY’, and ‘THE OVERLAND TELEGRAPH’S COMPLETION'.
Mintage 7,000