The oath of office, which is outlined in the constitution, has been said or affirmed by every single president who has held office since George Washington in 1789.

Celebrities plan to join the mayors of New York and Minneapolis to rally cities to chart their own course on health care, climate change and other issues during Donald Trump's administration, organizers said ahead of the inauguration-eve demonstration.

Ready for his big moment, Donald Trump swept into Washington on a military jet Thursday, kicking off three days of inaugural festivities.