It is January 1930 and the restless Southern Ocean is heaving itself up against the frozen coast of Eastern Antarctica as the exploring ship Discovery shoves its way through the pack. One of the key moments of the British, Australian, and New Zealand Antarctic Research Expedition (BANZARE)—is about to occur: the expedition is about to succeed in its primary mission. Douglas Mawson, the expedition's Australian leader, ascends to the island's bleak summit. There, he and his crew assemble a mound of stones and insert into it the flagpole they've carried with them across the ocean. Mawson reads an official proclamation of territorial annexation, the photographer Hurley shoots the moment on film, and one of the men hauls the Union Jack up the pole. In the freezing wind, the men take off their hats and sing "God Save the King." They deposit a copy of the proclamation into a metal canister and affix this to the flagpole. The men row back to the Discovery; Mawson returns to his cabin and writes up the event. A crucial moment in Antarctica’s spatial history has occurred: on what Mawson has aptly named Proclamation Island, Antarctica has been produced as Australian space. But how, exactly, does this production of Antarctica as a spatial possession work? How does this moment initiate the transformation of six million square kilometres of Antarctica—42% of the continent—into Australian space? The answer to this question lies in three separate, but articulated cultural technologies: representation, the body of the explorer, and international territorial law. This article attends to the ways in which these spatialising forces together 'nationalise' Antarctica by transforming it into Australian national space. Mawson's BANZARE performance on Proclamation Island is a moment in which the legal, the physical, and the textual clearly intersect in the creation of space as a national possession. Australia did not take possession of forty-two percent of Antarctica after BANZARE by law, by exploration, or by representation alone. The Australian government built its Antarctic space with letters patent. BANZARE produced Australia's Antarctic possession through the physical and legal rituals of flag-planting, proclamation-reading, and exploration. BANZARE further contributed to Australia's polar empire with maps, journals, photos and films, and cadastral lists of the region’s animals, minerals, magnetic fields, and winds. The laws of "discovery of terra nullius" and of "the spirit of possession" coalesced these spaces into a territory officially designated as Australian. It is crucial to recognise that the production of nearly half of Antarctica as Australian space was, and is not a matter of discourse, of physical performance, or of law alone. Rather, these three cultural technologies of spatial production are mutually imbricated; none can function without the others, nor is one reducible to an epiphenomenon of another. This article examines the ways in which six million square kilometres of Antarctic ice were, and continue to be, produced as Australian national space