What was the historical significance of electing Barack Obama president in 2008?

On November 4, 2008, Obama defeated the Republican nominee, Senator John McCain of Arizona, making him the President-elect and the first African American elected President. He was the third sitting U. S. Senator, after Warren G. Harding and John F. Kennedy, to be elected president. Upon the vote of the Electoral College on December 15, 2008, and the subsequent certification thereof by a Joint Session of the United States Congress on January 8, 2009, Barack Obama was elected President of the United States and Joe Biden Vice President of the United States, with 365 of 538 electors