The Very First DX – December 12, 1901

Marconi at 04.30 GMT on 12 December 1901, Guglielmo Marconi succeeds in sending the first transatlantic wireless communication demonstrating that radio waves transmissions could be transmitted across the Atlantic ocean, disproving detractors who told him that the curvature of the earth would limit transmission to 200 miles or less.

The Italian inventor received in St. John’s, Newfoundland, Canada, the letter S in morse code (three dots) transmitted from Poldhu, Cornwall, in England.

You can read the rest of the story at DX Zone.  Just being a little picky here but they keep referring that the signal was received at Newfoundland, Canada.  Newfoundland didn’t join Canada till 1949.