If anyone is going to be in Washington and plans to visit the Library of Congress, my friend who was there recently has some advice. He went into the LoC, then found out that ANYONE can get a library card, especially if they state that there’s something that they are researching, (e.g. anti-intellectualism in American politics). You don’t even have to be American.
However, the building where you join is across the street from the main library building and often has a line-up for entry; and if you go outside you have to leave security, line up, and enter security again (bag check?). However, the two buildings are connected by an underground tunnel. You can stroll over via the tunnel, staying within the secure area and skipping the line.
Second, he said that if you are reading something and want to continue the next day, there’s a room where you can leave your book overnight; because if you put it in the “return to shelves” area it can take a few days to get back it its place.
So if you’re going to be in D.C., you might want to get library cards!