In 1897 Nikola Tesla filed a patent for radio. However, Guglielmo Marconi filed for a similar patent the year before. Tesla gained the patent in 1900 but in 1904 The U.S. Patent office changed the patent and gave it to Marconi. It was not until 1943 that the U.S. Supreme Court ruled that Tesla was the true patent owner for radio.
For more milestones in the development of radio, see:
Source:“Who Invented Radio?” http://www.pbs.org/tesla/ll/ll_whoradio.html (accessed Setember 21, 2011).
Image Source: http://www.pbs.org/tesla/ll/ll_poevis.html.