Two important Washington museums, which are about to close for a three-year renovation, are sending many of their most important works on the road.

Both the National Museum of American Art and the National Portrait Gallery share an aging Greek Revival building in the heart of Washington. Andrew Jackson laid the cornerstone of the structure, called the Old Patent Office Building, in 1836. Lincoln held his second inaugural ball there weeks before he was assassinated, and Walt Whitman nursed wounded soldiers in its halls when it was a hospital during the Civil War.

But despite its rich history, it is in bad shape. Plaster is falling. Walls are cracked. Wiring is outdated. Heating and cooling systems are antiquated. For example, it is impossible to heat one part of the building while cooling another, something that is often required since paintings suffer if they're not kept at 70 degrees with 50 percent relative humidity.

During the $60 million renovation, the National Museum of American Art will circulate 500 of its artworks, including some of its finest masterpieces, to more than 70 museums. The first stop of its "Treasures to Go" tour will send 69 paintings and sculptures, including works by Georgia O'Keeffe, Marsden Hartley, Stuart Davis and Franz Kline, to the gallery at Florida International University in Miami. For a full schedule, check the museum's web site, link to www.nmaa.si.edu/treasures.

The Portrait Gallery, the smaller of the two institutions, expects to send four new exhibitions and several old one to roughly 30 cities, including some in Europe.

When the museums reopen in three years, they will have at least a third more public space because offices, conservation labs, library and storage areas have been moved to the nearby Victor Building, recently purchased by the Smithsonian Institution, which operates both museums. The museums now have separate entrances on opposite sides of the building's quadrangle, but when the renovation is complete, they will share a single entrance and lobby at Eighth and F streets NW.

During the shutdown, some works from the Museum of American Art will be displayed at the Renwick Gallery at Pennsylvania and 17th streets NW. The Portrait Gallery also plans to have some of its best known work on display at sites in Washington, too.