containing approximately 173 million items and employing over 3,000 staff. 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".

When Congress moved to Washington in November 1800, a small congressional library was housed in the Capitol. Much of the original collection was lost during the 1814 burning of Washington by British forces during the War of 1812.