Irene had at one time been a major hurricane, with winds higher than 110 mph as it headed toward the U.S. It was a tropical storm with 65 mph winds by the time it hit New York. It lost the characteristics of a tropical storm and had slowed to 50 mph by the time it reached Canada.
It never became the big-city nightmare forecasters and public officials had warned about, but it still had the ability to surprise.
The storm left millions without power across much of the Eastern Seaboard.
The 11-state death toll, which had stood at 21 as of Sunday night, rose as bodies were pulled from floodwaters and people were electrocuted by downed power lines.
The tally of Irene's destruction mounted, too. One private estimate put the damage up and down the East Coast at $7 billion.
Many of the worst effects arose from rains that fell inland, not the highly anticipated storm surge along the coasts.
In New England, landlocked Vermont contended with what its governor called the worst flooding in a century. Streams also raged out of control in upstate New York.
Residents of Pennsylvania and New Jersey nervously watched waters rise as hours worth of rain funneled into rivers and creeks.
There was flooding in Philadelphia where water rose 15 feet above normal in some areas.
Nearly 7.5 million homes and businesses lost power at some point during the storm. Lights started to come back on for many on Sunday, though it was expected to take days for electricity to be fully restored.
About 50,000 power customers in New York City went dark. The tropical storm knocked down trees and flooded parts of the city.
"First time it's ever flooded like this in the house," said New York flood victim Sidney Anthony. "It's up to our knees. The bed is floating, the chair is floating. Everything's floating."
The New York Stock Exchange and other businesses were open Monday. The subways and buses were up and running again in time for the morning commute.
President Barack Obama spoke Monday at the White House Rose Garden saying it will take time to recover from Irene, and he pledged the federal government would be doing everything in its power to ensure people have what they need to get back on their feet.
Obama said the response continues and promised to make sure the Federal Emergency Management Agency and other agencies do what they can to help people on the ground.
Irene was the first hurricane to make landfall in the continental United States since 2008, and came almost six years to the day after Katrina ravaged New Orleans on Aug. 29, 2005.
Irene affects travel plans
Airports in the Northeast are scrambling to get thousands of flights that were canceled over the weekend back on schedule. Nearly 12,000 flights were canceled nationwide over the weekend.
According to flight cancellation trackers, more than 1,600 flights were canceled on Monday. A flight tracking service estimates that 650,000 passengers have been stuck on the ground since Irene hit, but some experts think it's a million or more.
Since the cancelations are weather related, passengers had to pay for their own accommodations.
According to the Federal Aviation Administration online flight status system, all East Coast airports have reopened except for Teterboro Airport in New Jersey.
On Monday, Los Angeles International Airport was experiencing normal operating conditions. Passengers from canceled flights over the weekend were working to get on new flights, but it could take some time to get all passengers re-booked.
That means many travelers heading to-and-from the East Coast could still face long delays, and some could be stranded for days.
The Associated Press contributed to this report.