The Library of Congress is the largest library in the world and the de facto national library of the United States. It holds more than 144 million items, including vast collections of manuscripts, rare books, maps and other special collections, and since 1870 has been receiving all US-published material under copyright deposit.
Located on Capitol Hill, the Library comprises three main buildings: the Jefferson Building, Madison Building and the Adams Building. Underground tunnels link the three buildings as well as the Capitol Visitor Center. The locations of key reading rooms are as follows:
The Library has undertaken extensive digitisation of its collections, and many items are now available freely online. Still more material has been microfilmed and is available to researchers in that format to preserve the originals.
To obtain a reader's card as a researcher at the Library of Congress, you need to visit Reader Registration, located in the Madison Building, when you first arrive. It's free to register, but you must present official ID, so take your passport! The process itself is relatively quick, though in busy periods you may have to wait. You can pre-register for your card online, but you still need to go to Reader Registration to present ID and get your card before you can use the Library.
Once you have your card you will be able to gain access to the reading rooms and order up material to consult. Like the Bodleian, the vast majority of the Library's collections are kept in closed stacks and often offsite, and must be requested via the online catalogue to a reading room. If the item you have requested is onsite it will be delivered the same day; offsite requests will be delivered the next business day.
If you plan to consult manuscript or special collections materials, you are strongly advised to contact the appropriate reading room in advance of your visit. Contact details may be found on the page of the relevant reading room (see above), along with further information on any specific policies or restrictions that may be in place for those collections. Note that if the collection has been microfilmed it will be available to you in that format in order to preserve the originals.
The Library of Congress provides a lot of information for researchers on how to access and use the library on their website.