The Library of Congress was originally established as a research library for U.S. senators and representatives.

Today, the Library's Congressional Research Service (CRS) provides Congress with objective research and analysis, fulfilling more than 500,000 requests a year. Congress first established the Legislative Research Service as a division of the Library in 1914 and, with the enactment of the Legislative Reorganization Act of 1970, expanded its mission and renamed it the Congressional Research Service.

Making extensive use of the Library's unparalleled collections for research, CRS works exclusively for Congress by providing timely and confidential support to members and committees on all issues of interest to them, at all stages of the legislative process.

When Congress is interested in the laws of other nations, it looks to the Law Library of Congress, whose multi-lingual specialists provide analyses of foreign legislation. Created by an act of Congress in 1832, the Law Library provides analysis of foreign legislation for more than 200 countries. An online database, known as the Global Legal Information Network, allows the United States and other member nations to share laws, statutes, regulations and other legal materials in their original language.

The Library's general research collections are unparalleled. Specific reference services to Congress, scholars, and the public are provided through 22 reference centers or "reading rooms," dividing the voluminous collections by media or subject matter.