"It's really strange; it's been real quiet," Walls said. "The calls really dropped off" from more than 500 in 2009.
Most of the security calls were minor, such as unattended packages that turned out to be false alarms, lost children and the moving of barriers as the events ended.
An anti-abortion protester climbed a tree near the U.S. Capitol, yelled remarks during the swearing-in ceremony and was questioned by U.S. Capitol Police.
D.C. Police Chief Cathy Lanier said the crowds appeared larger than the advanced estimate of 500,000 to 700,000, and she had to dispatch more officers to the gates to help deal with crowding.
Protesters made traffic worse by demonstrating at major thoroughfares like K and 16th streets and forcing police to shut down those areas.
At least three children were reported missing in the chaos. One of them had been found as of 4 p.m.
Airspace within a 30-mile radius of the Capitol was closed, and more than 2,600 police officers from across the country had been sworn in to help secure the event. Florida state troopers wore earmuffs for the first time.
More than 6,000 National Guard troops, many with camouflaged Humvees, helped manage the crowd and move traffic.
That helped the D.C. police department's 3,800 officers, as well as agents from the Secret Service, FBI, Homeland Security and ATF.
The U.S. Secret Service agents who helped coordinate police and military personnel were pleased with the cooperation and planning of the dozens of agencies involved, as well as the behavior of the more than hundreds of people who poured onto the National Mall.
"It's been uneventful, and that's the way we like it," said spokesman Ed Donovan.
Information from Examiner staff writers Naomi Jagoda and Alan Blinder as well as the Associated Press was used in this report.