01/25/2011 07:14 pm ET Updated May 25, 2011

State Of The Union History: Unforgettable Moments From Past Addresses

As President Obama prepares to deliver his second State of the Union address, now is a great time to see which speeches get remembered and why.

Presidents are not required to give speeches. Article II, Section 3, of the Constitution simply mandates that the president "shall from time to time give to the Congress Information on the State of the Union, and recommend to their Consideration such measures as he shall judge necessary and expedient." Presidents such as Thomas Jefferson, Truman, Eisenhower, Carter, and Nixon all sent their messages in writing. Reagan even canceled his speech in 1986 after learning of the explosion of the space shuttle Challenger.

But most modern presidents have elected to deliver the speech, using it as an opportunity to introduce sweeping agendas or restore confidence in struggling ones. And while some leaders have successfully shaped their presidency with the speech, issuing great words that have gone down in history, other speeches are more remembered for embarrassing gaffes or controversial reactions from the audience.

Unforgettable State Of The Union Moments