I don't think the Library of Congress is a public library. Public libraries need financial support from the central or local governments and are open to all the public. However, the Library of Congress was established as a research library of the American legislature according to the US Congress Act, and it is a special reference library for members of Congress and senior government officials. Although it has been opened to the outside world, its basic nature has not changed. The New York Public Library is the largest public library in the United States.