There are already over 2 million digital objects from America's libraries, archives and museums in the collection. It will continue to grow in terms of the quantity of objects in the collection and also the ways these objects can be filtered and presented.
From the site itself:
"The Digital Public Library of America brings together the riches of America’s libraries, archives, and museums, and makes them freely available to the world. It strives to contain the full breadth of human expression, from the written word, to works of art and culture, to records of America’s heritage, to the efforts and data of science. "The use of open data and APIs will mean that the contents and collections can be further harnessed in the future to create new tools and methods of research. Five related apps are already available from the DPLA site. One of these allows cross searching of DPLA with Europeana, a similar initiative and portal for digital objects and collections from European libraries and museums.
The site itself has various built-in functionalities allowing the user to view collections by location, chronologically or to explore as exhibitions covering subjects such as the Great Depression and US Activism.