The inventor of the wireless telegraph, which is also known as radio, was an American dentist named Mahlon Loomis. In 1866, he demonstrated this technology by making a meter attached to a kite move another kite. The patent for wireless radio transmitter technology, however, is held by Nikola Tesla.
At the same time as Nikola Tesla's patent filing, two other inventors took out patents on wireless radio transmitters. One of them was Guglielmo Marconi, an Italian inventor credited with the first successful wireless telegraph message across the Atlantic. This first transatlantic wireless telegraph message was of the letter "S" and was sent from England to Newfoundland in 1902.