The announcement came Thursday from the committee, which has pledged to make Obama's inauguration "the most open and accessible in history."
People who can't get the 240,000 tickets to the swearing in on the Capitol grounds can fill the mall. In the past, parts of the mall have been closed off as a parade staging area. Inaugural parade participants will be announced next week.
The Park Service said it's expecting at least 1 million people for the inaugural, and the city has put the number as high as 5 million.
Those who watch the swearing-in on the Mall will be able to watch and listen to the ceremony on large screens.
"This will be an Inauguration for all Americans," said District Mayor Adrian Fenty in a press release. "And so we are dedicated to opening it up so that people from across the country can gather together in America's front yard. We remain hard at work to ensure the day's festivities are safe and accessible for visitors, residents, and businesses alike."