The Thomas Jefferson Building, also known as the Main Library, is the oldest of the Library of Congress buildings in Washington, D.C. Built between 1890 and 1897, it was initially known as the Library of Congress Building. In 1980, the building was named in honor of Thomas Jefferson, a Founding Father, the principal author of the Declaration of Independence, and the third U.S. president. In 1815, Jefferson's donation of his own book collection formed a core foundation for the library's collection.

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".