The Mellon family already released 48 other artworks during Rachel Mellon's lifetime, including Van Gogh's painting Green Wheat Fields, Auvers in December. Most of the museum's Van Gogh works will be displayed together in June.

The Mellon acquisitions were made mostly in the 1950s and 1960s, with many brought back from France. Most works kept in their Upperville, Virginia, estate haven't been seen since a 1966 exhibition of the Mellon Collection.

Other highlights include one of Monet's earliest known paintings, Still Life with Bottle, Carafe, Bread and Wine from 1862-63 and a large, colorful painting by Degas titled The Riders, depicting a group of jockeys on horseback.

The collection includes 12 oil sketches by Georges Seurat, who died young and did not have a large body of work. Now, combined with four other paintings by Seurat and a drawing, the museum has one of the most significant collections of his work in the United States, Jones says.

There are nine American paintings in the Mellon group, including two by Winslow Homer.

Since 1964, Paul and Rachel Mellon have donated nearly 1,200 works of art to the museum. Mellon's father, the Pittsburgh industrialist Andrew Mellon, founded the National Gallery in 1937 and donated his famous art collection to the nation.