Article II of the U.S. Constitution, which establishes the powers and duties of the president, says in Section 3 that:
He shall from time to time give to the Congress information of the state of the union, and recommend to their consideration such measures as he shall judge necessary and expedient.
President Obama will do that tonight in a manner that, in many ways, has shallower historical roots than you might realize.
You’ll note that the constitutional language doesn’t mention a speech. George Washington and John Adams did address the Congress with their thoughts on the “state of the union” or SOTU. But the shy, wordsmith Thomas Jefferson decided to send his thoughts in writing in 1801. (I prefer to think it was about shyness. Jefferson claimed that a president addressing Congress had a monarchical quality because of the tradition of the “speech from the throne” in which the kings or queens of England address the opening session of a new Parliament.)
The written SOTU message continued for more than a century (although the document was usually read aloud to the House by a clerk, with no one listening). Some of the written SOTUs dealt with huge matters. In the middle of the Civil War, Abraham Lincoln devoted most of his written 1862 SOTU message to a pitch for a constitutional amendment that would have offered federal to compensation to any slave state that was willing to emancipate its slaves before the year 1900. Yikes.
Finally, after 112 years of no SOTU speeches, the professorial Woodrow Wilson decided to revive the spoken message in 1913, and he kept it up throughout his first term. But the first to break the spoken message streak was Wilson himself, who was too incapacitated by health problems to give an address in 1919 or 1920. His successor, Warren G. Harding, gave spoken SOTUs, but then came “Silent” Calvin Coolidge. Coolidge gave one SOTU speech (the first to be broadcast over radio) in 1923, then went back to the written tradition. Herbert Hoover never gave a spoken message.
It’s really Franklin D. Roosevelt who strengthened the speechifying tradition. It was during his long tenure that the speech was dubbed the “State of the Union” address. All of his were broadcast over radio, and in 1936 he was the first to deliver the address in the evening (when he could reach a bigger radio audience), and he used his 1941 SOTU to introduce his famous “Four Freedoms” theme.
Since FDR, almost every president has delivered a nationally broadcast, evening speech almost every year. Harry Truman’s address in 1947 was the first to be televised.
The big exceptions are years of presidential transitions. Outgoing presidents have the option of giving a last SOTU address, submitting a final message in writing or neither. The last four presidents have chosen to do neither.
The incoming president gives an inaugural address which, while not delivered to the Congress, tends to serve a similar purpose. Starting with Ronald Reagan in 1981, incoming presidents have all given a speech to a joint session of Congress after their inaugurals in which they outline their legislative goals, but these are technically not considered State of the Union sddresses.
The tradition of giving a spokesperson for the opposition party TV time shortly after the president’s address, to give a response, dates from 1966.
The American Presidency Project has lots more SOTU history.