The bulk of the Northern Territory's population not living in Darwin lies along its track. South Australia Stuart Highway passes through the Far North region to Port Augusta. The highway passes through the Woomera Prohibited Area where travellers may not leave the road. The highway continues south-east towards Adelaide. History Background John McDouall Stuart led the first successful expedition to traverse the Australian mainland from south to north and return, through the centre of the continent, in 1861–1862. In 1871–72 the Australian Overland Telegraph Line was constructed along Stuart's route. The principal road from Port Augusta to Darwin was also established on a similar route. A track developed along the route of the telegraph, and by 1888 the road between Adelaide and Alice Springs was well known. Several wells along the route provided water, although these could run dry or be contaminated by dead animals, resulting in sections as long as without water. The route was traversed by motor vehicles in the 1920s. While passable, sections of the road could be sandy, boggy, washed away in the winter, or rugged with boulders. Several creek crossings were required, though few were difficult. North of Alice Springs the road was in comparatively good condition, with sections allowing speeds of up to . Highway planning and construction With the onset of World War II, supply roads leading to the north of the country were considered vital by the Federal Government. A central north–south highway was planned to connect the railheads at Alice Springs and Birdum, with surveying completed in August 1940. The task of constructing the highway was split between the Main Roads Departments of three states, to ensure completion before the next wet season. New South Wales would construct the northern section of , Queensland the central section of , and South Australia the southern section of . The Alice Springs–Birdum road was completed by December 1940, – upgraded from an often impassable track to an all-weather sealed highway that could cope with heavy military traffic. The highway was built in under than 90 days. In one week, was constructed, which was claimed to be a world record. The new highway, in conjunction with the railways at either end, reduced the impact of Darwin's isolation. Quick and efficient movement of military equipment and troop was possible, with the road remaining open throughout the wet season. By March 1941, military authorities advocated extending