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On Tuesday, January 28, President Obama will deliver his sixth State of the Union address to Congress and the American people. The speech has become something of an annual tradition in Washington-though it's not actually required to be delivered with such regularity-and this year it comes at an important time for the president as he seeks to inject some energy and optimism into what some say has been a disappointing second term. Here are five things to know about the State of the Union address.

1.) The guidelines for the address are written in the Constitution… but they're rather vague. Article II, section 3 of the U.S. Constitution states: "He shall from time to time give to Congress information of the State of the Union and recommend to their Consideration such measures as he shall judge necessary and expedient." There is no further guidelines given for frequency of delivery and no description of how Congress is to be given said information. The practice of delivering an annual address in person before Congress started with George Washington, but was discontinued by Thomas Jefferson in 1801, and wasn't revived until Woodrow Wilson in 1913. Jefferson's reason for discontinuing the practice was that he believed the structure too closely resembled the British tradition of the "speech from the throne"- where in the reigning monarch delivers an address to the members of Parliament.

2.) A letter suffices in this case. Of course Jefferson and the men who followed him as president were still required to check in with Congress occasionally, and they did this by writing letters which were read to the members of Congress by a clerk. This practice still continued occasionally past Wilson's revival of the in-person speech: Presidents Truman, Eisenhower and Nixon delivered written State of the Union letters during their tenures.

3.) There have been two presidents who never delivered a State of the Union. William Henry Harrison, who only served 32 days in office, and James A. Garfield, who served for 199 days, were not in office long enough.

4.) It's not entirely clear when the title "State of the Union" was coined. Although the phrase is written out in the Constitution, for over a century the practice of updating Congress on the state of affairs was referred to as "the President's Annual Message to Congress." In 1934 Franklin Delano Roosevelt referred to that year's message as the "Annual Message to Congress on the State of the Union." And according to the House of Representative's Clerk's office, the speech has been referred to as the State of the Union since 1947. But when referring to the speech as such became common is not clear.

5.) The opposing political party's televised response after the speech, known as the opposition response, is a modern development. The first so-called opposition response was given in 1966 by Republican Sen. Everett Dirksen and then Rep. Gerald Ford, in response to Lyndon Johnson's State of the Union. The speech then became a regular practice for the party not in the White House, and is now viewed as a possible launchpad-a chance for a rising star in the party to make an impression on a large cross-section of the American population. Two of the public officials who gave the speech later went on to become president- George H.W. Bush in 1968 and Bill Clinton in 1985.

Tune into "This Week" on Sunday for a look at what to expect in Tuesday night's address.