Video from the scene showed the much larger Atlantic Asphalt tanker hit the cruise boat while it was docked as metal and glass crashed and crunched.
Tugboat operators, nearby workers, police and several other rescuers rushed to help. New Orleans Mayor Helena Moreno called it “a miracle on the Mississippi.”
The mayor said 32 people were taken to the hospital, but none of them had critical injuries.
The boat started listing within minutes and flipped while emergency workers were still trying to get everyone off the ship.
Dozens of people on board and at least two police officers were dragged from the 66-degree Fahrenheit (19-degree Celsius) river onto nearby ships.
Devon Flanagan was at his job nearby at the Port of New Orleans when workers rushed down the dock. He got out of his truck and saw the American Heritage on its side and passengers in the water.
“It was just chaos,” he said. “You had all types of ships, like other barges and other companies down there trying to help out, which also was a little convoluted because you had people still in the water.”
The cruise ship was built in 2015 and operated by American Cruise Lines. It is five stories and can hold up to 150 passengers.
The American Heritage was finishing an eight-day cruise to several Mississippi River destinations in Louisiana and Mississippi.
The cruise line said it was working with the Coast Guard and would share more information when it can.