Washington (CNN) As President Donald Trump took the podium Tuesday evening for his address to a Joint Session of Congress, his confirmed Cabinet members were all on hand -- except one. Department of Veterans Affairs Secretary David Shulkin was appointed the designated survivor, per an administration official. The designated survivor goes to a distant, secure and undisclosed location outside of Washington while everyone else gathers to listen to the President's address in the Capitol. The designated survivor must be eligible to be president, and if a higher-ranking successor survives a potential incident, that person would become president ahead of the designated survivor. The practice started in the 1960s during the Cold War when there were fears of a nuclear attack.