Short answers, pulled from the story.
Andrew Jackson Higgins directed the construction of a massive industrial complex at the village of Michoud, Louisiana in 1940. The project cost $180 million and was built on behalf of the United States government for World War II production.
NASA took management of MSFC Michoud Operations in 1961 and renamed it Michoud Assembly Facility in 1965. From September 1961 through December 1972, the factory built first stages of Saturn I and Saturn IB rockets.
Tank ET-122 ended up being the last even though its sequence number was lower than the total number of tanks produced because it had been damaged during Hurricane Katrina and required repairs prior to completion. Debris from the storm also damaged the stored tank inside the main manufacturing building.
Thirty-eight NASA and Lockheed Martin employees stayed behind during Hurricane Katrina to operate pumping systems and pumped more than one billion gallons of water out of the facility to prevent destruction. Each employee who stayed received the NASA Exceptional Bravery Medal which is NASA's highest bravery award.
A ceiling height limitation of 12 meters ruled out construction of the larger Saturn C-8 vehicle there. This physical constraint became a major reason why the smaller Saturn V was chosen over the originally planned Moon vehicle.