An estimated 2 million people attended the event, according to federal authorities. The record crowd resulted in an unprecedented security effort, including more than 30,000 police and military personnel.
The attendance topped the 1.2 million people who were at Lyndon B. Johnson's 1965 inauguration, the largest crowd the National Park Service has on record.
By 7 a.m., much of the Mall was filled with people and police opened the checkpoint for spots along the Inaugural parade route, ending the long lines that had formed.
At least five suburban parking lots for the region's subway system — the second largest in the country — were filled by 5 a.m.