"This building is home to many of our national treasures," Bush said at a dedication ceremony for the museum which has been put through a two-year, $85 million facelift.
"It is a reminder of our country's proud heritage," the president said.
The nearly 200-year-old Star-Spangled Banner is the centerpiece of a dramatic new gallery.
Architects also have reorganized the central core of the museum to make it easier to navigate and to help visitors find the history they're looking for.
With the museum responsible for holding and caring for more than three million objects, favorite exhibits, such as Dorothy's ruby slippers from "The Wizard of Oz," will again be on view. Other displays representing iconic moments in U.S. history include the Woolworth's lunch counter from Greensboro, N.C., that became a symbol of the nation's civil rights movement in 1960 and a statue of George Washington.
The renovation of the 44-year-old Smithsonian Institution landmark was accomplished with $46 million in federal funds and $39 million in private donations. Before the overhaul, the museum had become one of the more tired-looking and outdated in the Smithsonian collection.
Part of the re-opening ceremony included a naturalization ceremony for five new U.S. citizens.