Libraries have been lending books to the public for thousands of years.[1] First libraries date back to 2600 BC during Sumerian civilization. In the modern era lending books largely happens by Public Libraries. Generally worldwide public libraries are non-profit organizations offering book lending services free to their patrons and are generally funded through taxes and donations or by the state.,[2][3] Public libraries are accessible to general public and are run by civil servants, state employees, or volunteers. Some of the largest libraries in the world include Library of Congress in the United States of America[4] and British Library[5] with millions of titles in their catalogs. Besides the public libraries, private libraries also provide lending services, and are usually run by individuals, associations, or by corporate organizations and universities. Private libraries usually require a subscription or membership to the library (paid or unpaid) and provide services specific to the organization, area or university.[citation needed]