The Library of Congress has the largest collection of materials in the U.S., and possibly the largest collection of legal materials too. The Library of Congress Web site (www.loc.gov) posts in formation about the library, including its formidable online catalog.
If you have a question, you can call the Library's general Reference Desk (202-707-5222) or their Legal Reference Desk (202-707-5080).
Catalog: The LOC posts an catalog that is comprehensive starting in 1968. Earlier records have been entered selectively. To do a thorough search of pre-1969 materials requires looking through the Main Card Catalog located on the first floor of the Jefferson Building.
Congressional Research Service (CRS): See the separate entry for "Congressional Research Service Reports."
Copyrights: The U.S. Copyright Office is part of the Library of Congress. For copyright information, see "Copyrights."
Document Delivery: The Library has a Duplication Services department (202-707-5640), but they take four to six weeks to make photocopies. In other words, unless you can easily get to the Library, most of the time you'll have to hire a document retrieval service or find another source. Companies that regularly make copies at the Library of Congress include National Corporate Research (800-494-5225), Penco (800-690-7362 or 703-912-9080), Independence Legal Support (240-392-0017 or email@example.com), and FSI Research (202-257-7722); for other companies, see "Washington, D.C. Document Retrieval."
Interlibrary Loan: The Library of Congress is a "lender of last resort." That is, you should try to borrow materials from other libraries first. If you can't find something they have anywhere else, though, the Library of Congress will lend to other libraries. The Library posts the relevant policies, contact information and ILL news.
The first step to borrowing from the LOC is to visit First Time Registration for ILL and fill out an online registration form. Once you are registered, you can place orders directly, and the LOC will send out materials when they are ready. For faster service, you can can hire a document retrieval service, such as National Corporate Research (800-494-5225), Penco (800-690-7362 or 703-912-9080), FSI Research (202-257-7722), Independence Legal Support (240-392-0017 or firstname.lastname@example.org), or a competitor. You can find a few other companies in the "Washington, D.C. Document Retrieval" entry.
Legislation: The Library also runs the Thomas web site, which posts bills, Congressional Committee information, the Congressional Record and more useful information about Federal legislation. The Library is developing a successor to Thomas called Congress.gov.