President Obama took the Oath of Office in a small, private ceremony at the White House on Sunday morning.
Under the Constitution, the president begins a new term on January 20th even if that's a Sunday. It's happened only six other times in American history.
Earlier, Vice President Joe Biden was sworn in by Supreme Court Justice Sonya Sotomayor.
On the National Mall, final preparations were underway for tomorrow's public ceremony and parade. As the Hardings of Northeast Philadelphia found, it's an impressive sight to see firsthand.
"It's hard not to get caught up in it. It's pretty cool. You see all these people, people from all over the country," said Paul Harding.
On Sunday, tourists roamed around without any problems but on Monday security will be very tight.
An estimated 800,000 people are expected to be on hand - about half the crowd of four years ago.
Still, they'll come with smartphones and cameras. Temporary cell phone towers will accommodate the demand.
Gilbert Wilson brought his family from Camden to witness history for a second time.
"Never see this again in my lifetime probably so this time I am seeing it and I want my children to be with me to watch this," said Wilson.
Action News caught up with Mayor Michael Nutter along the National Mall. He attended Sunday's private swearing in ceremony for Vice President Joe Biden.
Mayor Nutter spoke with President Obama last week and says the president is ready to tackle a fresh agenda in the next four years.
"I see a fire in his eyes. I think he is very focused on the future and trying to get stuff done, and I think that's what people want here in Washington," said Mayor Nutter.
Mayor Nutter will be seated on the steps of the Capitol during the ceremony.
The Gorman family from Media was also lucky enough to get tickets to see the big event up close.
"Oh, we love Obama. We just love him so much, and we're Democrats. We just wanted to be here in the city," said Mary Gorman.
Meanwhile President Obama will be using two Bibles during Monday's ceremony. One of them was owned by Abraham Lincoln, the other by Rev. Martin Luther King Jr.