Monday marked the passage of six difficult years of rebuilding for the region, which is showing signs of a strong recovery from the costliest natural disaster in U.S. history. The storm killed more than 1,800 people, a majority of them in New Orleans where water filled up the city after levees and floodwalls built by the Army Corps of Engineers failed.
Despite the hardships, many residents were upbeat.
"We're coming back, one house at a time, just like the community was built so many years ago," said Ronald Lewis, 60, who lives in New Orleans' Lower 9th Ward and runs a Mardi Gras Indian museum called the House of Dance and Feathers. He was one of the first residents to build back after Katrina.
To commemorate those lost in Katrina, Lewis and his Original Big 9 Social Aid and Pleasure Club marched a second-line down one of the only streets rebuilt in the neighborhood's worst-hit area and hung a new wreath on an oak tree for one member's mother and niece killed in the storm. The wreath changing has become a yearly ritual for the anniversary.
It wasn't an altogether sad event, with people coming out of their homes to dance to the music and greet friends.
Tamika Shelling, a 32-year-old bus driver who grew up in the Lower 9th, sat and waited for the second-line to pass. Since Katrina, she doesn't live in the neighborhood anymore, but she likes to return on the storm's anniversary because it's an occasion to see old friends, neighbors and family. "You see a lot of people you haven't seen in years," she said.
Also Monday, New Orleans Mayor Mitch Landrieu and his sister, U.S. Sen. Mary Landrieu, D-La., joined hundreds of people for a walk to the top of a bridge in the Lower 9th Ward where a bouquet of flowers was tossed into the Industrial Canal. The floodwalls along the canal burst open during Katrina and led to deadly flooding.
Similar events were held elsewhere on the Gulf Coast. In Biloxi, Miss., the names of storm victims were read aloud as about 100 people gathered in prayer at the Katrina Memorial site on the Town Green.
At the University of New Orleans, the commemoration was more academic than emotional at a symposium to discuss a new book on the recovery by the Brookings Institution and the nonprofit Greater New Orleans Community Data Center. The meeting focused on government and civic improvements driven by a populace that's more engaged since the catastrophe.
"The region is well positioned to be a model of rebirth as long as it doesn't let this early progress slip," said Amy Liu, of the Brookings Institution, and an editor of the book "Resiliency and Opportunity."
The reforms in New Orleans include the creation and funding of an inspector general's office to oversee city contracting and an independent police monitor to help reform a scandal-plagued police department; a complete overhaul of the education system and a proliferation of independently run charter schools; and an evacuation system that takes into account the needs of those without cars or easy access to transportation.
Panelists said Katrina provided an emotional impetus that allowed reform efforts to gain traction.
"There's about a one-letter difference between an engaged citizenry and an enraged citizenry," said Tulane University's David A. Marcello, author of a chapter on ethics. "And rage unquestionably fueled a considerable amount of the reform impulse and the engagement that came after Katrina."
"You can't sustain rage or engagement indefinitely," Marcelo added. "You have to use those moments to create systems that will endure."
Despite other troubles that have beset the region, such as last year's oil spill, it looks like the Gulf Coast is on the mend.
Mississippi Gov. Haley Barbour said that six years ago it looked like "the hand of God had wiped away the coast." Today, he continued, visitors to the Mississippi coast "can't tell anything ever happened because it's been rebuilt."
"Naysayers predicted our city's best days were over. We knew better," said U.S. Rep. Cedric Richmond, D-New Orleans.
Still, residents and politicians alike acknowledged there's a lot left to do.
President Barack Obama promised to help the region "come back stronger than before" while praising "the grit and determination" of the Gulf Coast's residents. He said his administration helped the recovery along by cutting red tape to free up recovery money and broke "through gridlock" to help thousands of displaced families find homes.
Still, it's not as rosy in many neighborhoods like the Lower 9th Ward where the recovery has been very slow. The neighborhood has lost about 14,000 residents.
"It's pretty slow," said Henry Holmes, the 77-year-old owner of Eatin' At Holmes, a restaurant he ran before Katrina. Without flood insurance for his business, he said he had spent his savings to get his restaurant reopened. "Unless it picks up, I'll have to close in five, six months."
Despite the hopeful tone of many of Monday's events, statistics released Sunday by Brookings point to numerous longstanding problems laid bare and exacerbated by Katrina, including high poverty, unaffordable housing and racial inequities.
And some in the city question the reforms touted by city leaders. At the UNO forum an audience member complained that the post-Katrina takeover of most New Orleans schools by the state cost thousands of teachers their jobs. Several people complained that the state should have re-opened the once-flooded Charity Hospital rather than plan for a new hospital that remains controversial and is years from opening.
Mayor Landrieu addressed some of the prickly issues at the symposium. Post-Katrina school changes, he said, have resulted in increased test scores and a narrowing of the gap in performance between blacks and whites. And he touted his administration's opening of local health clinics around the city.
"Collectively, we as a people have found a way to begin major systemic change," he said.