The water was sloshing up to the top of the Liberty Island sea wall by 11 a.m. on October 28, 2012, the day the Statue of Liberty was being dedicated following an extensive renovation project carried out by the Princeton firm Mills + Schnoering Architects. Members of the firm were on hand to help celebrate the completion of what was arguably one of their most important undertakings.

“It actually opened for half a day on that Sunday, accommodating some crowds,” Michael Mills, a partner in the firm, recently recalled. “The Secretary of the Interior and lots of dignitaries were there. It was quite an event. But Hurricane Sandy was already gearing up. And the next day, it came in and tore up the island.”

It took eight months to fix the damage caused by the monster storm. The docks, snack bar, electrical systems, and walkways were destroyed. Several buildings on the island were gutted, though the statue itself was unharmed. About 500 people had to be laid off. But by July 4, 2013, the site was officially reopened to the public.

During repairs from the storm, small generators were used to keep the statue illuminated at night until electricity could be restored.

For Mills + Schnoering, the brief dedication ceremony came after several years focused on the site. What started as a relatively simple assignment involving the staircase up to the statue’s crown evolved into a much larger task. “This was a very quick, three-month project to make the stairs up to the crown much safer,” Mr. Mills said. “It was fairly small from a design and construction standpoint. But it was also kind of a test, in a way. I think we made the National Park Service very comfortable with the idea of giving us the more significant project.”

The firm was charged with replacing the elevator and installing a new emergency elevator, designing new stairs, higher railings, reopening a closed entrance, and making the site accessible. “It was very complicated. It took a year to build and two years to design,” Mr. Mills said. “We added a ton of mechanical, too.”

Formerly known as Fort Wood, Liberty Island once housed a land battery in the shape of an 11-point star that was later used as the base on which the statue now sits. The 225-ton statue, designed by sculptor Frederic Auguste Bartholdi, was given by France to the United States for the 1886 centenary celebration. Alexandre-Gustave Eiffel, who later created the Eiffel Tower, designed the metal skeleton supporting the sculpture.

The historic site was closed for a year while work progressed. The architecture firm, which is known for its historic preservation projects, was given a full historic structures report by the National Park Service, helping them to understand the site’s significance. A surprise discovery during construction was an old armory, which they preserved.

Much of the challenge of renovating the site came from the constraints of the monument. “The idea of getting two separated fire stairs and an elevator into a space 27 feet square, and crisscrossed by the Eiffel girders that you’re not allowed to touch, presented a huge challenge,” Mr. Mills said. “Those girders were there to support straps that came down from the statue to hold her down in a high wind.”

The location in the middle of an island in New York harbor required very -specific planning and logistics. Because the docks had been destroyed by the storm, the contractor figured out a way to land at the island by hiring a World War II landing craft, Mr. Mills said. “The contractor did a wonderful job of getting materials out there. They had to deal with not only taking everything out by boat, but also the security concern,” he said. “Every boatload that went out was checked by men and dogs in Jersey City and on the island when it arrived.”

For Mills + Schnoering, the goal of the project was to make the experience of touring the statue safe and less claustrophobic. By using protective glass in some locations, they were able to create a sense of open space that had previously not existed.

Thanks to Hurricane Sandy, the story of the project became more about the recovery than the project itself. But now that the site is reopened to visitors and several months have passed, the focus is back where it belongs. “This was a very special project for us,” Mr. Mills said. “It took a long time. But hopefully, the results speak for themselves.”