The reopening was a sign of recovery as the nation used the day to celebrate its independence in a wide variety of ways from a solemn fireworks tribute to fallen firefighters to traditional parades and concerts to competitive hot dog eating.
In New York, a large crowd gathered for the holiday and ribbon-cutting ceremony at Liberty Island with federal officials and Mayor Michael Bloomberg. Lines stretched blocks long for the boat, which left from Battery Park in Manhattan.
On Liberty Island, some repairs to brick walkways and docks are ongoing but much of work has been completed since Sandy swamped most of the 12 acres (5 hectares) of the national landmark.
The statue was spared in the fall storm, but Lady Liberty's island took a serious beating. Railings broke, docks and paving stones were torn up and buildings were flooded.
The storm destroyed electrical systems, sewage pumps and boilers. Hundreds of National Park Service workers from as far away as California and Alaska spent weeks cleaning mud and debris.
In his weekly radio address, Obama urged Americans to live up to the words of the Declaration of Independence by securing liberty and opportunity for their own children as well as for future generations.
The first family was to host US servicemen and women at the White House for a cookout later today.