Louisiana ? A Navy assault ship built with tons of steel salvaged from the World Trade Center towers began its journey to New York on Tuesday, sailing down the Mississippi River in a pea-soup fog as watchers along the levee strained for a glimpse.

The USS New York, named to commemorate the Sept. 11 terrorist attacks, left the Northrop Grumman shipyard where it was built for the trip to its namesake city. The $1 billion ship will be formally commissioned in New York in early November.

The New York is 684 feet long and can carry up to 800 Marines. It has a flight deck that can handle helicopters and the MV-22 Osprey tilt-rotor aircraft.

Four tugboats performed an intricate set of maneuvers to pull the warship from the dock at the New Orleans-area shipyard and turn it 180 degrees toward the waters of Gulf of Mexico. An armed Coast Guard speedboat and a helicopter flying overhead guarded the vessel. The ship will sail through the Gulf and around Florida before turning north and continuing to New York.