Haddon Corner, Survey marker and heritage site at Queensland-South Australia border intersection

Haddon Corner is marked by a circular dark grey metal plaque set in a ring of coarse pale stone on reddish ground. Raised capitals curve along its top edge reading QUEENSLAND, with HADDON CORNER in a straight line below; SOUTH AUSTRALIA curves along the bottom edge. Angled metal bars radiate from a small central pin, and a raised N sits at the left edge.

Haddon Corner was marked in 1880 by surveyor Augustus Poeppel during the official survey of the western Queensland–South Australia border carried out in 1879–1880. The corner defines the north-eastern angle between the two states at the 26th parallel south and the 141st meridian east. Its marking was described as a surveying feat of its time. The site was added to the Queensland Heritage Register on 9 November 2012.

The Karuwali language region takes in the landscape around Haddon Corner and the locality of Betoota, within the Diamantina Shire Council boundaries. The corner itself was marked in 1880 during the official survey of the western Queensland border, a line that cut across this country.

The site is located in a remote, arid region requiring careful preparation before visiting. Bring plenty of water and supplies, and use a sturdy vehicle since roads in this area are basic and distances between services are considerable.

The plaque's raised letters read QUEENSLAND along the top and SOUTH AUSTRALIA along the bottom, with HADDON CORNER across the middle and an N at the left edge. Angled metal bars radiate from a small central pin, and pale splotches mark the weathered dark grey surface. The marker was added to the Queensland Heritage Register on 9 November 2012.