One of the Museum's most important collections consists of over 56,000 photo negatives of significant and rare works across Europe and America. This project was commissioned by Helen Clay Frick beginning in 1922. Many of the works photographed are lost, damaged, or destroyed today, making the photos that much more valuable. These photos can be accessed online (see the link below).
The Library played a significant role during World War II as it served as the base for the Committee on the Protection of Cultural Treasures in War Areas of the American Council of Learned Societies. This Committee sought to find and preserve important works that were located in areas devastated by the war. They accomplished this by producing maps showing the location of significant works of art across Europe. During this time, the Library shut down to focus its resources on this effort. This is the only time in the Library's history that it closed its doors for a significant amount of time.