A website has been set up to help US museums check whether their collections include art stolen by the Nazis.
Much - but not all - of the art looted by the Nazis was recovered
The Nazi-Era Provenance Internet Portal goes online on Monday, allowing people to check art that disappeared in Europe between 1932 and 1946.
So far 66 museums have given details of their collection to the site, including the Metropolitan Museum of Art in New York and Chicago's Institute of Art.
The Nazis were thought to have looted more than 1.5 million pieces of art.
More than 100,000 items of museum quality are still missing, and some of them are said to have made their way to the US.
The site has been set up by the American Association of Museums. They have so far catalogued 5,761 items from the New York and Chicago museums, and plan to list another 1,600.
The site will be linked to similar catalogues in Europe.
Edward H. Able Jr, the association's president, said that 17 claims had been settled by US museums over stolen art since 1997.
These included a Degas pastel at the Art Institute of Chicago, and a Henri Matisse painting that had been at the Seattle Art Museum.
Mr Able said the list included more than just art museums.
"We have museums of all kinds - an item could have seeped into a history museum, for example," he said.
As well as stealing art from countries they occupied, the Nazi regime also forced art dealers to sell items from Jewish or anti-Nazi owners at artificially low prices.
As well as paintings, these items also included such things as books, religious objects, stamp and coin collections, furniture and other antiques.