Doing Research at the Library of Congress

II. Searching the Catalog With Library of Congress Subject Headings

When you wish to search the Library's online catalog by subject, you have to come up with the correct headings appropriate to your topic. Often, the category terms used by the catalog are not the same as the keywords you might think of on your own. For example, books on "test tube babies" are not found under that phrase; the proper term is Fertilization in vitro, Human. Similarly, the heading for books on resistance movements in Italy in World War II does not use the word "resistance"; the proper term is World War, 1939-1945--Underground movements--Italy and its various subdivisions. Books on multinational corporations are grouped under the term International business enterprises. Works on "moonshining" are cataloged under the heading Distilling, illicit. Searching the catalog by any keywords other than these exact headings will result in your missing most of the books on these topics.

The Library's purpose in creating standardized subject headings is to round up works on a particular subject in one place, so that you will not have to think up endless keyword synonyms and variant phrases, or foreign language terms, that authors have used in their titles. Books on the subject of the Bay of Pigs invasion, for example, have titles such as the following:

All of these (and many other) variant title-keyword books are rounded up under the single subject heading Cuba--History--Invasion, 1961. Of the nearly ninety catalog records under this heading, more than half do not use the words "Bay of Pigs" in their titles or note fields--and so would be entirely missed by a keyword search on that phrase.

The most important point is this: subject headings are not the same thing as keywords. The former are standardized terms that are artificially created and added to catalog records (not merely transcribed from the books themselves) by professional catalogers, in order to create retrievable points of commonality among topically related records that would otherwise be widely scattered by their many different keywords. The approved list of these terms is called Library of Congress Subject Headings (LCSH); it is an annually revised multivolume set of books, often referred to simply as "the red books" because the binding of the set is always of that color. The primary purpose of LCSH is to provide standardized English-language subject category terms that can be used to bring together in convenient groups the literature of the world--no matter how great its variation in title keywords, and no matter what the original language of the works being cataloged--so that materials on the same subject can be noticed and retrieved together.