 List of the largest libraries in the United States

The size of libraries in the United States is determined by a number of metrics, including number of holdings (in terms of volumes or titles held), by circulation (i.e., library materials checked out or renewed); or by number of library visits.The largest public library in the United States—and the second largest library in the world—is the Library of Congress in Washington, D.C., which is the "de facto" national library of the United States.