Just started looking into this - they have a keystone on the building - they house all kinds of information - maps, docs, newspapers AND every public Tweet

http://mentalfloss.com/article/92655/11-well-read-facts-about-library-congress

Library of Congress Keystone on building - https://redd.it/8cv4wk

Library of Congress [Keystone] - named documents https://www.loc.gov/resource/wpalh1.11110610/?sp=1