On inauguration day, Donald Trump will take part in a tradition that dates back more than 200 years to George Washington: the delivery of the inaugural address. It will be his first speech as the 45th president of the United States. During the divisive campaign, Trump was known for veering from prepared remarks and rallying the crowd with impromptu chants. For the inauguration, his aides say the speech will focus on national unity. The speech will also be short, possibly under 20 minutes (The longest inaugural speech was delivered by William Henry Harrison, the ninth US president. It was one hour and 45 minutes long, clocking more than 8,400 words). From JFK and Reagan to Clinton and both Bushes, unity has been a common theme in many inaugural speeches. The president is usually gracious to his predecessor, and also provides the country a vision for the future. Watch our video to learn about the other components that have made up inaugural speeches.