CLOSE When President Trump addresses a joint session of congress Tuesday night, he will undoubtedly say that the State of the Union is strong, and he's right. The economy is growing, the stock market is booming, and unemployment is low. USA TODAY 
 
 President Trump and Agriculture Secretary Sonny Perdue, this year's designated survivor. (Photo: Mark Humphrey, AP) 
 
 WASHINGTON – And this year's "designated survivor" is ... Agriculture Secretary Sonny Perdue. 
 
 Perdue, a former governor of Georgia, will sit out President Trump's State of the Union address at the U.S. Capitol, waiting for the worst. 
 
 For decades, presidential administrations have selected one Cabinet member to stay away from State of the Union speeches attended by the president and his staff, in case disaster strikes and wipes out the line of presidential succession. 
 
 During the speech, the designated survivor is taken to a safe, secure, undisclosed location. The identity of the official is kept secret until just before the speech, when his or her absence would be apparent. 
 
 When Trump spoke to a joint session of Congress in February of 2017, Veterans Affairs Secretary David Shulkin sat out the event as the designated survivor. 
 
 The tradition harkens back to the dawn of Cold War, amid fears of a nuclear exchange with the Soviet Union. 
 
 Its roots are in the Presidential Succession Act of 1947, which outlines who would assume the presidency in the case of a catastrophic event such as a nuclear attack. 
 
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 After the vice president, the speaker of the House, and the president pro tempore of the Senate, the line of succession goes to cabinet secretaries in the order they were created, beginning with the secretary of State and ending with the secretary of Homeland Security. 
 
 One member of Trump’s cabinet cannot serve as a designated survivor: Secretary of Transportation Elaine Chao. She was born in Taiwan and does not meet the constitutional requirements to serve as president. 
 
 The selection of a designated survivor was relatively routine and unremarkable until the terrorist attacks of Sept. 11, 2001, when the practice took on new urgency. 
 
 Hollywood has long been fascinated with idea, from a 2000 episode of NBC's The West Wing to the current ABC series actually entitled Designated Survivor, in which Kiefer Sutherland plays a Cabinet member who assumes the presidency after a terrorist attack on a State of the Union address wipes out the rest of the other possible successors. 
 
 Read or Share this story: https://usat.ly/2E3ywp8 ||||| Every member of President Trump’s Cabinet was invited to attend his first State of the Union address on Tuesday night – except one, Secretary of Agriculture Sonny Perdue. 
 
 Perdue was named "designated survivor" just hours before Trump is expected to step up to the podium to deliver his address to Congress. 
 
 Ahead of the speech, Perdue will be taken to a secure and undisclosed location outside of Washington, D.C., where he is expected to stay with Secret Service agents until the conclusion of the event. When Trump and his Cabinet members safely exit the packed House chamber, Perdue will be allowed to return home. 
 
 Here’s what you need to know about the "designated survivor," a unique role that has been around for decades. 
 
 What does it mean to be the "designated survivor?" 
 
 During major political events, such as a presidential inauguration or State of the Union address, an official within the presidential line of succession is given the role of "designated survivor" and has to stay away from the event. 
 
 This precaution is taken to assure continuity in the presidency. 
 
 If a catastrophic event were to strike the Capitol and result in the death or disablement of the president, vice president, speaker of the House or other White House officials, then the "designated survivor" could step in to be the acting commander-in-chief. 
 
 When did this tradition begin? 
 
 This tradition dates back to the 1960s amid concerns of a potential nuclear attack during the Cold War. 
 
 But official records of "designated survivors" weren't kept until 1984, starting with Secretary of Housing and Urban Development Samuel R. Pierce Jr. during Ronald Reagan's State of the Union speech on Jan. 25, 1984. 
 
 Who has been chosen as the "designated survivor" over the years? 
 
 Perdue has been appointed the "designated survivor" for Trump's 2018 address. As secretary of agriculture, Perdue would ordinarily rank low in the line of succession to the presidency – ninth on a list of 17 officials. 
 
 It's not unusual for a lesser-known Cabinet member to be selected, as the president may point out higher profile officials as he mentions specific tasks and initiatives in his speech. 
 
 Department of Veterans Affairs Secretary David Shulkin was given the role during Trump's address to a joint session of Congress in 2017. 
 
 Here's a list of Cabinet members who were named "designated survivors" and did not attend the State of the Union over the past 10 years: 
 
 Jan. 30, 2018: Secretary of Agriculture Sonny Perdue 
 
 Jan. 12, 2016: Secretary of Homeland Security Jeh Johnson 
 
 Jan. 20, 2015: Transportation Secretary Anthony Foxx 
 
 Jan. 28, 2014: Energy Secretary Ernest Moniz 
 
 Feb. 12, 2013: Energy Secretary Steven Chu 
 
 Jan. 24, 2012: Agriculture Secretary Tom Vilsack 
 
 Jan. 25, 2011: Interior Secretary Ken Salazar 
 
 Jan. 27, 2010: Sec. of State Hillary Clinton and HUD Sec. Shaun Donovan 
 
 Jan. 28, 2008: Secretary of the Interior Dirk Kempthorne 
 
 Jan. 23, 2007: Attorney General Alberto Gonzales
– As the last i's are being dotted on President Trump's State of the Union address, one traditional formality has been announced: Agriculture Secretary Sonny Perdue is this year's "designated survivor." That means if disaster strikes during the speech, wiping out the entire presidential line of succession, the 71-year-old will be in charge of the country, reports USA Today. Perdue is expected to be hanging out with Secret Service agents at a secure location until the event is over, per Fox News.