Libraries are the memory of humankind, irreplaceable repositories of documents of human thought and action. The New York Public Library is such a memory bank par excellence, one of the great knowledge institutions of the world, its myriad collections ranking with those of the British Library, the Library of Congress, and the Bibliothèque nationale de France. Virtually all of the Library's many collections and services are freely available to all comers. In fact, the Library has but one criterion for admission: curiosity.

The combination of scholarly research collections and a network of community libraries lends to the Library an extraordinary richness. It is special also in being historically a privately managed, nonprofit corporation with a public mission, operating with both private and public financing in a century-old, still evolving private-public partnership. The research collections (for reference only, they are located in four major centers for research) are similar to the holdings of the great national and university libraries, and the community circulating libraries (located in neighborhoods throughout the Bronx, Manhattan, and Staten Island) resemble classic American municipal libraries.

Today the Library's online catalog and website make its holdings accessible to users worldwide. The Library's collections themselves reflect the profoundly democratic and all-encompassing nature of the institution. Numbering into the tens of millions, its holdings range from the most venerable monuments of human culture — such as the Gutenberg Bible and Jefferson's manuscript copy of the Declaration of Independence — to materials that document the everyday lives of otherwise anonymous people.

All these features, taken together, make The New York Public Library an irreplaceable and complex institution, wonderful to use but not always easy to grasp. A useful way to understand the Library is to consider its beginnings and subsequent evolution. It has been very much a creature of time and place, bearing the imprint of its origins but always, like any living organism, coping with struggles and problems while adapting to an ever changing environment.