NEW ORLEANS (AP) -- The Gulf Coast is marking the sixth anniversary of Hurricane Katrina with commemorations to honor those killed during the catastrophic storm that left New Orleans and dozens of coastal towns in Mississippi, Alabama and Louisiana devastated.

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, residents are upbeat.

Ronald Lewis, who lives in the Lower 9th Ward, says the area is coming back one house at a time.

2011 The Associated Press.