The Library of Congress (LC) is the research library that officially serves the United States Congress and is the de facto national library of the United States. It is the oldest federal cultural institution in the United States. The library is housed in three buildings on Capitol Hill in Washington, D.C.; 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.