Western Australia border

The Western Australian border was originally designated as 129th meridian east longitude (129° east). However, the border marked on the ground is some distance from this line.Kununurra is the closest town to the Western Australian border, being about 25 km west of the border. The closest settlement is Border Village, 1,734 km to the south on the South Australian side of the border, on Eyre Highway.

The Western Australian (WA) border marked on the ground, is not as straight as it looks on a map. The Northern Territory border with Western Australia and the South Australian border with Western Australia are displaced east-west by approximately 127 metres, due to errors within the limits of surveying technology available in the 1920s.

Where Western Australia meets the Northern Territory (NT) and South Australia (SA) borders is a 127-metre segment running east-west along the 26th parallel south latitude (26° south).

In June 1968, two monuments were erected to mark each end of this 127-metre segment, At the easternmost of these concrete border markers all three borders meet, at Surveyor Generals Corner.

In 1788 Governor Phillip claimed the continent of Australia only as far west as the 135th meridian east (135° east) in accordance with his commission. (26 January 1788 – MAP)

It has been suggested that the 1788 claim by the British of 135° east was in reference to Spain's claims under the Treaty of Tordesillas. Spain was seen as no longer having an interest in the area. On the other hand, the other signatories to the treaty, the Portuguese still had a presence in Macau and East Timor. Adoption of 135° east as a boundary would minimise provocation of the Portuguese. By 1825, however, Britain was powerful enough and found it convenient to adopt the original line of the Portuguese under the treaty, 129° east.

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Wikipedia