According to the History Channel, "Franklin Roosevelt ... was the first president to appear on TV – from the World's Fair in New York City on April 30, 1939. FDR's speech had an extremely limited TV audience, though, airing only on receivers at the fairgrounds and at Radio City in Manhattan."
The subject of the above–referenced History Channel article is "the first–ever televised presidential address from the White House", which was made by Harry S. Truman on 5 October 1947. His purpose was "[to ask] Americans to cut back on their use of grain in order to help starving Europeans." There was concern that the Marshall Plan would not be enough to prevent famine in war–torn Europe, and Americans were asked to eat less meat, eggs and bread. In the event however, the Marshall Plan was a success and these additional measures were not required.
Although the number of television sets in American homes were still numbered in the thousands at the time, rather than millions, every subsequent speech that Truman made from the White House was televised (according to the History Channel). In 1948 he became the first presidential candidate to broadcast a paid political advert, and his 1949 inauguration address was the first to be televised.
© Haydn Thompson 2021