The story begins with a fire. When the British burned the Capitol in 1814, the Library of Congress - founded fourteen years earlier as an in-house reference shelf for legislators - went with it. Thomas Jefferson sold his personal library to the government the following year to replace it. The 475 law titles in Jefferson's collection became the new seed of what would eventually grow into the Law Library. Of those, 318 had been published in England - the dominant source of legal precedent for an English-speaking republic that had only recently broken away from the system it inherited. State laws and decisions from outside Virginia were almost entirely absent, in part because Jefferson had classified them as foreign law. The categorization carried a certain Virginia-centric logic. It also meant that for decades, the Library would struggle to gather American legal materials from states whose practice differed from Jefferson's.

Through the 1820s, lawyers in Congress repeatedly proposed creating a dedicated Law Library. The bills failed each time. On January 20, 1832, New York Senator William L. Marcy, himself a former associate judge on the New York Supreme Court, introduced legislation directing the Librarian to prepare an apartment for a law library and remove the law books from the general collection into it. Marcy's bill passed both houses, and President Jackson signed it on July 14, 1832. The statute remains in force. The first appropriation was $5,000, with $1,000 for each of the next five years - selection of books to be made by the Chief Justice himself. Some 2,011 volumes were transferred from the general Library of Congress collection to form the new nucleus, 693 of them from Jefferson's original donation. The Justices of the Supreme Court were granted statutory authority to make rules for the use of the library during sittings of the court - a relationship that would endure for a century.

The Law Library's home from 1860 to 1897 was the former Supreme Court Chamber, the dim semi-basement room beneath the new chamber where the Court now sat. The Law Librarian's 1898 annual report described it without sentiment: about 50 feet square. This cockpit, dim-lighted and inconvenient. The justices used it, members of Congress used it, gentlemen of the bar arguing cases used it, and law students used the few tables that remained. Each could sign out up to three books. A reserved collection of major texts sat aside for the exclusive use of the justices. The space served everyone who needed it and pleased no one. By 1897, the new Library of Congress Building - now called the Thomas Jefferson Building - was finally open, and the Law Library moved upstairs into the newly built complex. The cockpit days ended.

American territorial expansion forced the Law Library to start collecting outside the Anglo-American tradition. The Louisiana Purchase of 1803 brought a property law system rooted in French civil law. The acquisition of Florida in 1819 added Spanish civil law to the mix. After the Mexican War in 1848, Congress directed the Library to acquire all available laws of Mexico - the first systematic foreign-law collection. Through the second half of the nineteenth century, the major European codes joined the shelves. In 1902, Librarian of Congress Herbert Putnam proposed a comprehensive index to the legislation of every country on Earth. He argued it could become an instrument of the highest value to the practical legislator. Congress refused to fund it. The project survived anyway, in fragments, decade by decade. By the late 1920s, the staff had started a card index of Latin American laws that would eventually be published as a two-volume Index to Latin American Legislation in 1961, with supplements running through 1975. Today the Directorate of Legal Research employs foreign-trained lawyers from around the world.

The collection moved with the rest of the Library of Congress into the James Madison Memorial Building in 1981 - 1.6 million volumes shifted over the course of four months. The reading room opened on the Madison Building's second floor in April that year. The numbers today are staggering: 2.9 million volumes of primary legal sources, 102 million microforms, 99,000 reels of microfilm, more than 3 million pieces of microfiche, and growing electronic holdings. It is the largest law library in the world. Congress still has first call on its services. The Supreme Court, since establishing its own library in 1935, draws on the Law Library mainly for foreign and international research - the global perspective that the in-house Supreme Court Library does not maintain. The Custodian of Law no longer climbs a staircase. The questions still come down, though, and the answers go back up - through reference desks, research reports, and the daily Global Legal Monitor that tracks legal developments from every jurisdiction the Directorate of Legal Research can reach.