Do you ever have trouble finding a particular book or resource in your school library? It’s OK if you do. Most libraries have tons of books, and librarians are there to help you find the things you need.

If you think your school library has a lot of books, though, wait until you learn about the nation’s largest library. Its amazing collection of books and resources will blow your mind!

What library are we talking about? The Library of Congress, of course! Built in 1800 in Washington, D.C., it’s the largest library in the world in both shelf space and number of books.

The Library of Congress is the official research library of the United States Congress. It’s also considered to be the national library of the U.S. It currently consists of three buildings in the nation’s capital.

When it was first started, the Library of Congress was housed in the U.S. Capitol. It stayed there throughout most of the 1800s until it moved to its current site.

Most of the library’s original collection was destroyed during the War of 1812. Thomas Jefferson replenished the library’s collection, though, by selling his entire personal book collection — over 6,000 books! — to the library in 1815 for $23,950 (that was A LOT of money way back then).

Over time, the Library of Congress continued to expand. Eventually it came to consist of the three buildings it is housed in today. Its main purpose is to research issues for members of Congress.

The Library of Congress is open to the public, but very few people are allowed to check out books. These privileged few include library employees, members of Congress, Supreme Court justices and other high-ranking government officials.

The Library of Congress holds much more than just books. Its various collections include more than 150 million items on over 800 miles of bookshelves. These items include over 34 million books, over 3 million recordings, over 13 million photographs, over 5 million maps, over 6 million pieces of sheet music and over 66 million manuscripts!

Among these millions of items are some of the most interesting and rare books in the world. In fact, the Library of Congress has over 700,000 rare books, which is the largest collection in North America.

The smallest book in the Library of Congress is Old King Cole. Measuring 1/25 inches by 1/25 inches, it’s about the size of a period at the end of a sentence. Its pages can only be turned using a needle!

The largest book in the Library of Congress is a 5 foot by 7 foot picture book featuring thousands of color images of the country of Bhutan. The Library also has one of only three perfect copies of the Gutenberg Bible, which is one of the most valuable books in the world.


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    • That’s OK, Rahul! We’re proud of you for guessing…we appreciate that! We’re also super glad you stopped by today’s Wonder to learn more about the Library of Congress! :-)

  1. This was a WONDERful Wonder!!!! I love reading and going to our library!
    I think tomorrow’s Wonder is about buttons.

    • How cool that you love reading and visiting the library, Annie! We do, too! Thank you for sharing your comment with us today and also for taking a guess at what you think tomorrow’s Wonder will be about! :-)

    • It makes us super happy to hear that you love books, Hannah! We’re glad you thought today’s Wonder was cool, too! Thanks for letting us know that! :-)

    • You’re absolutely right, Sydney! Way to go! We thought it was FUN to learn about all the millions of items that are housed in this HUGE library. We hope you did, too! :-)

    • Yes it is, Shundee! Thanks for sharing something awesome you learned about the Library of Congress in Wonderopolis today! :-)

    • WOW, we’ve got some super smart Wonder Friends who are sharing what they know about the Library of Congress today! Thanks for being one of them, Keundra! We appreciate your comment! :-)

    • That’s OK, Hannah! Join us here in Wonderopolis tomorrow and we’ll find out together what tomorrow’s Wonder of the Day® will be! :-)

    • That’s really AWESOME, Lois! Did you get to visit lots of different places inside the library and also see special books and artifacts? We think it must have been a GREAT experience for you…thanks for sharing about it! :-)

  2. Cool. I never knew that the world’s biggest library is in the U.S.A. My cousin lives there. Maybe she has heard of it.

    • We bet your cousin has heard of the Library of Congress if she lives in Washington, D.C., Caelah! It must be a lot of fun to live in such a historical place and get to explore so many cool museums, monuments and LIBRARIES whenever she wants to! :-)

  3. This video gave a lot of interesting information about the library. We would like to visit the Library of Congress because the video made it sound cool! Some questions we have: Are you allowed to just read books there like in our own library?
    Also, are there any children’s books on the shelves? Do they get new releases, too? We would like to know! Thank you, Wonderopolis!

    • Those are all SUPER questions about the Library of Congress, Mrs. Alaniz’s 4th Grade Class! We invite you to visit the Library’s website and explore to WONDER even more! Here is a link to the Library’s “Young Readers Center” page: We think you will like it a LOT! :-)

  4. Does the Library of Congress have a copy of every book in the world? We really found the wonder interesting and looked online for pictures of the LOC. What do you mean by tomorrow’s wonder being as cute as a button? We think Microsoft is a great resource. See you tomorrow!

    • You guys ROCK for WONDERing more about the Library of Congress on your own, Mr. Draper’s Class! We’re super proud of you! “CHECK OUT” these Frequently Asked Questions visitors have when they visit the LOC (we think you will REALLY like the answer to #4 on the list): :-)

    • It’s so WONDERful to hear from you again, Josh! We hope you have been having a GREAT school year at Kerrick Elementary! Thanks for letting us know you liked the video for today’s Wonder! :-)

    • Thanks for taking a guess about tomorrow’s Wonder, “Wonder!” We can’t wait to visit Wonderopolis tomorrow to see if your guess is correct! :-)

  5. We think tomorrow’s Wonder might be about puppies, babies, kittens, or about how buttons are made.

    We did not know the Library of Congress was so enormous! Wow!

    • Hello, Miss Kirsten’s Kindergarten GT Class! It was LOTS of fun to learn how GINORMOUS the Library of Congress is, wasn’t it? It really gives our brains a workout to WONDER how they fit so many millions of items inside! Thanks for visiting Wonderopolis today! :-)

    • We’re so glad you think so, Anna! We like hearing how our AWESOME Wonder Friends like you enjoy learning new things in Wonderopolis! :-)

    • We can’t even imagine what it’s like to keep track of over 800 miles of bookshelves, can you, B Flures? That’s a LOT of books and other items! Thanks so much for hanging out in Wonderopolis with us today and learning about the Library of Congress! :-)

    • We think that ROCKS, Isaiah Betty! Thanks for being such a WONDERful Wonder Friend and visiting us at school AND at home! :-)

    • It makes us SUPER happy to hear that you love learning in Wonderopolis, Shyear! Thanks for leaving us such a GREAT comment to let us know that today! :-)

    • That’s a really great guess about tomorrow’s Wonder, Lima Bean Machine! We think learning some cool new things about buttons sounds like FUN! Thank you for stopping by today’s Wonder of the Day®, too! :-)

    • That’s right, Tristin! Great job! We hope you enjoyed learning about the Library of Congress as much as we did today! :-)

    • Hello, jadariedwards! On yesterday’s Wonder, Rahul guessed that today’s Wonder would be about grocery stores. Even though his guess was off by a bit, we still think it was creative and ROCKED! We think all of our Wonder Friends (like you and Rahul) ROCK, too! :-)

    • We thought it was cool to learn that AMAZING fact, too, John! We are still trying to imagine where they put all those books (more than 34 million of them)! :-)

    • You’re quite right, Cody, and we’re SUPER glad you like learning in Wonderopolis…we like learning here, too! :-)

  6. Hi wonderopolis. I loved reading about “The Biggest Library in the World.” I learned that. The biggest library in the world is “The Library of Congress”.(the library that congress mostly has) Thomas Jefferson sold his personal book collection to this library for 23,950 dollars, after most of the books in library were destroyed in the war of 1812. Plus there is this book called” Old King Cole” the smallest book in the library 1/25 of a inch by 1/25 of a inch. I knew that library are big and have tons of books, just not as big, and as many books as this library. I am still wondering how big is the library foot by foot, just for my knowledge. Thank you wonderopolis for this amazing article. I loved it.

    • We’re glad you enjoyed exploring this Wonder about the Library of Congress so much, Team Unger 5! We did, too! Can you imagine turning the pages of such a SUPER small book as “Old King Cole?” It would be a lot of FUN! If you’d like to learn more about the Library of Congress and the buildings that house it, you can visit this cool page on the Library’s website: :-)

    • Thanks for sharing more about your cousin, Caelah! We think it’s really cool that you both live in different countries, but both countries are in North America! We hope you have an AWESOME week! :-)

  7. Hello,

    Just so you know, I go on wonderopolis every day and I love learning new things. I learned two new words and they are manuscript and congress. I did not know that it has over 150 million books or that it is in Washington D.C. I think that tomorrow’s wonder is WHO INVENTED BUTTONS.

    • Thanks SO MUCH for letting us know you visit Wonderopolis every day, Team McNeil 12! We REALLY appreciate hearing that (it makes our hearts smile!)! We think it ROCKS that you love learning new things, too! Wonderopolis is a GREAT place to do that! :-)

  8. Hello,

    I learned two words and they are congress and manuscript. I did not know that the library had over 150 million books. I thought that was interesting, I also though about how it is in Washington D.C. That’s cool, too.


    • We’re glad you had a GREAT time learning about the Library of Congress by exploring this Wonder, Team McNeil 12! Way to go! Thanks for always WONDERing about the world around you! :-)

    • We appreciate you letting us know that you liked today’s Wonder of the Day®, Lolita! Thanks for sharing that with us! :-)

  9. I’ve been wondering a lot about the moon lately. Could tomorrow’s wonder be about the unseen “dark side” of the moon?

    • That’s a GREAT question, Cody! Did you know that many of the ideas for our Wonders of the Day come from amazing Wonder Friends just like YOU? You can let us know what you WONDER about by clicking on the “nominate” link that’s found at the top of every page in Wonderoplis and answering a few easy questions! It’s FUN to nominate ideas for future Wonders! We hope you’ll give it a try! :-)

  10. I never even knew there was a library that was that big! It’s humongous! Do people give you ideas for what questions you do?

    • Hey, Emaline! It’s GREAT to hear from you today! Many of the ideas for future Wonders of the Day come from the AWESOME, WONDERing minds of our creative Wonder Friends! Did you know that YOU can tell us what you WONDER about anytime you like by leaving us a comment or by clicking on the “nominate” link at the top of every page in Wonderopolis and answering a few quick questions? It’s super easy and LOTS of fun…we hope you’ll give it a try! :-)

    • Thanks for leaving us such a nice comment, Amoolya! We really appreciate that you think Wonderopolis ROCKS! :-)

  11. Hello WONDERopolis,
    We picked this wonder because this wonder gives us more information about the wonder!

    We never knew there was a library so big in the whole wide world!

    Bye wonderopolis

    :) :) :)

    • Wouldn’t it be LOTS of fun to LEARN in a big library like that, Kayla and Audrey? We think so! Thank you BOTH for leaving us such a SUPER comment today…you are AWESOME! :-)

    • HOORAY, we’re so glad you’re WONDERing with us, Nicole H! We hope you have the opportunity to visit the Library of Congress in the future! :)

  12. Wow! What a big library. I cannot imagine owning over 34 million books. That is a lot of reading! What is the 2nd largest library in the entire world? And I found it very interesting that someone would make a book as small as a period at the end of a sentence. Is that book even possible to read? I would love to visit that library. I love reading, but I wouldn’t even know where to start!

    • Hi, Dom! Thank you so much for your comment. We are in the process of changing the content of this Wonder. Thanks, again!

  13. As Dom said The British Library is the largest in the world carrying well over 170 million items.
    The US Congress Library comes second with only around 158 million items.

    • Hi nottsboy! We are working on updating the information in this WONDER. Thanks for making us aware and thanks for visiting WONDERopolis! :)

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Have you ever wondered…

  • Where is the largest library in the world?
  • When was the Library of Congress built?
  • How many books does the Library of Congress have?

Wonder Gallery

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Try It Out

Ready to check out your local library? It may not be the largest library in the world. In fact, it might be quite small. But that’s OK. Even the smallest library can offer valuable information and exciting adventures.

If you don’t already have a library card, ask for one! A librarian will be happy to get you signed up, so you can take advantage of your local library’s resources.

If you don’t know the depth of offerings available at your local library, ask for a tour. A librarian can show you that there’s so much more than books available.

Many libraries have music and movies to check out, as well as computers to use. There may also be special events, including story times and even arts and crafts classes.

So get to know your local library! Where else can you borrow great books, beautiful music and interesting movies for free?


Still Wondering

Visit EDSITEment! to learn more about the Folger Shakespeare Library, a British research institution that contains authentic editions of Shakespeare’s works!


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