The Boston Public Library is a municipal public library system in Boston, Massachusetts, founded in 1848. The Boston Public Library is also Massachusetts' Library for the Commonwealth, meaning all adult residents of the state are entitled to borrowing and research privileges, and the library receives state funding. The Boston Public Library contains approximately 24 million items, making it the third-largest public library in the United States behind the federal Library of Congress and New York Public Library, which is also privately endowed. In 2014, the library held more than 10,000 programs, all free to the public, and lent 3.7 million materials.

The Library of Congress (LOC) is a research library in Washington, D.C., that serves as the library and research service of the U.S. Congress and the de facto national library of the United States. Founded in 1800, the library is the United States's oldest federal cultural institution. The library is housed in three elaborate buildings on Capitol Hill. It also maintains a conservation center in Culpeper, Virginia. The library's functions are overseen by the Librarian of Congress, and its buildings are maintained by the Architect of the Capitol. The Library of Congress is one of the largest libraries in the world. Its collections contain approximately 173 million items, and it has more than 3,000 employees. Its collections are "universal, not limited by subject, format, or national boundary, and include research materials from all parts of the world and in more than 470 languages".