The “20th Century Heritage” distinction was established through a campaign launched by the French Ministry of Culture and Communication in 1999. It “identifies to the general public, by means of a specially conceived logotype, buildings and urban complexes whose notable architectural and urban characteristics are highlighted for future generations as extraordinary examples of our 20th century heritage”.
For Laurence Engel, current president of the Library, “it is more than just a distinction for the National Library of France, it is the artistic recognition by the Ministry of Culture and Communication of this important architectural construction, already well received by critics and visitors of Paris. […] The site of the National Library of France François Mitterrand has long made a long-lasting impression. The project is a tribute to books and knowledge, therefore to the cultural history that the National Library of France carries with it.”
Origins :
http://www.culture.gouv.fr/documentation/memoire/VISITES/labelxx/lieu_frameset.htm
http://www.lefigaro.fr/livres/2017/06/02/03005-20170602ARTFIG00294-la-bnf-francois-mitterrand-recompensee-par-le-label-patrimoine-du-xxe-siecle.php