I often find photos for books and articles on the Library of Congress site. I just found out the buildings are haunted. Check it out.

From DC Hauntings:

The Library of Congress is a lesser known haunted building on Capitol Hill. It does have its share of ghosts however. The most told ghost story is the police officer who resides in the stacks. He has been seen in both his uniform as well as his casual clothes. He has helped several people exit the stacks when they have become lost in the miles and miles of books. According to the description of the man (and his name, as he tells people) he was a sergeant who died several years ago. This occurrance is well known among many library employees. Other occurrances in the library's main building include doors opening by themselves, constant banging on the steps, and a mysterious dark haired man. One of the strangest recent events happened about three years ago when some painters were doing some work in the north corridor on the second floor. The area was closed to the public, and the workers needed get a cart by two heavy curator cases. One case moved about a foot, all by itself, allowing the workers to get the cart through.