The Harvard Library system comprises about 73 libraries, with more than 18 million volumes. It is the oldest library system in the United States and the largest university library and largest private library system in the world. Based on number of items held (including musical scores, maps, prints, recordings, etc.), it is the fifth largest library in the United States; based only on volumes (generally books), it is the third largest, after the Library of Congress and Boston Public Library.

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