It was first observed by ground-based measurements from Halley Bay on the Antarctic coast, during the years 1980-84. [Farman, Gardiner and Shanklin.] (At about the same time, an ozone decline was seen at the Japanese antarctic station of Syowa; this was less dramatic than those seen at Halley since Syowa is about 1000 km further north, and did not receive as much attention.)  It has since been confirmed by satellite measurements as well as ground-based measurements  elsewhere on the continent, on islands in the Antarctic ocean, and at  Ushaia, at the tip of Patagonia. With hindsight, one can see the hole beginning to appear in the data around 1976, but it grew much more rapidly in the 1980's.