Historians and other scholars classify sources as primary or secondary. Once you have identified a possible research topic, you will need to use both types of sources. We usually start working with the secondary sources first, to see what other historians have said about the topic, then start our search for primary sources to use as the basis for our own interpretation.
Primary sources are produced at the time of the event or phenomenon you are investigating, and they purport to document it. They reflect what someone observed or believed about an event at the time it occurred or soon afterwards. These sources provide the raw material that you will analyze and interpret. Primary sources can be published or unpublished (archival).
In general, published primary source material covers a wide range of publications, including first-person accounts, memoirs, diaries, letters, newspapers, commentaries, statistical reports, government documents, court records, reports of associations, organizations and institutions, treatises and polemical writings, chronicles, saints' lives, charters, legal codes, maps, graphic material (e.g., photographs, posters, advertising images, paintings, prints, and illustrations), literary works and motion pictures. Some of these materials were not published at the time of their creation (e.g., letters), but have subsequently been published in a book.
There are different types of primary sources for different historical periods. Church documents and saints' lives serve as primary sources for the study of medieval history, while newspapers, government reports, and photographs serve as primary sources for the modern period. What constitutes a primary source depends in part on how you have formulated your research topic. In other words, there is really no intrinsic or distinguishing feature of a text that makes it a primary, rather than secondary, source. Many sources, whether visual or textual, can serve as either primary or secondary sources. The key is how you use the material. In order to determine whether a source might be primary or secondary for your purposes, you must consider it in relation to your particular topic.
Here's an example of how a source can serve as either primary or secondary. Let's say you are studying the Chicago race riots of 1919. You find some articles by historians published in the 1950s and 1960s in the Journal of American History and the Journal of Negro History, theorizing the causes of the riots. These might be used as secondary literature representing various scholars' interpretations of the events of the summer of 1919 in Chicago. Or you may use the same articles as primary sources revealing historically situated concepts of racial violence.
You can find published primary sources by using the online catalog and published bibliographies. You can also look at secondary literature on your topic (see below) to ascertain what sources other scholars have used in their research. Remember that there is nothing in the online catalog record for a book that indicates whether it is a primary or secondary source, since this is not necessarily an inherent or essential characteristic.
The UIUC Library also has some unpublished primary source material (archives and manuscripts), but this is a relatively small body of material compared to the abundance of published primary sources held by the Library. Most of the Library's unpublished primary source material will be found in the University Archives, located in the basement of the main Library, or the Student Life and Culture Archive, located east of the President's house on Florida Avenue in Urbana (1707 S. Orchard St.).
The University Archives, located in the basement of the main Library, houses the largest collection of historical manuscripts in Illinois. Both personal papers and organizational or institutional records are held in the University Archives. Examples include the papers of the journalist James B. Reston (reporter for the New York Times from 1939 to 1989), the papers of Avery Brundage, the president of the U.S. Olympic Committee (1929-52) and International Olympic Committee (1952-72), and the recently acquired papers of Leon Dash (reporter for the Washington Post from the 1960s to 1998, and a Peace Corps volunteer in Angola). Among the organizational archives held in the University Archives are the records of the Advertising Council, the agency established in 1942 as the War Advertising Council to build support for the war effort through public service advertising. (Last year a graduate assistant in the University Archives prepared an exhibit on the "People's Capitalism" campaign conducted by the Advertising Council with the U.S. Information Agency in 1956.) More information is available about the holdings of the University Archives and the Student Life and Culture Archive at their websites.
Secondary literature includes scholarly books, articles, and essays (both analyses by contemporary scholars as well as older analyses), surveys, criticism, comparative studies, reference sources, and works on theory and methodology. When we talk about secondary sources, most of the time we are referring to the published scholarship on a subject, rather than supplemental or auxiliary material (bibliographies, encyclopedias, handbooks, etc.). This scholarship is analytical and interpretive. It may synthesize the work of other historians to present a totally new interpretation. More likely it offers a new reading of previously analyzed sources or presents an analysis of previously unknown sources.
Hence you use secondary sources to identify the main currents of thought on your topic. Which historians have taken up this topic and what were their main arguments? How has our understanding of the subject changed with shifts in the predominant methodologies and theoretical perspectives in the historical profession?
Secondary sources are published as books, chapters in books, and journal articles. Books can be single-authored [e.g., Politics, Culture and Class in the French Revolution, by Lynn Hunt] or produced by several scholars working in the same or related fields [e.g., The Invention of Pornography: Obscenity and the Origins of Modernity, 1500-1800, edited by Lynn Hunt].
To identify secondary literature, you can do subject searches in the online catalog to find books or subject searches in article databases to find articles. You can also consult standard published bibliographies (e.g., the American Historical Association Guide to Historical Literature) and specialized bibliographies (Steven Pressman, Poverty in America: An Annotated Bibliography).
You can also look for review essays, in which a historian who specializes in the subject analyzes recent scholarship; you may find more lengthy historiographical treatments of the topic published as chapters in collections, journal articles, or even monographs; you can read about the topic in a subject encyclopedia and look at the bibliography at the end of the entry; and you can find a major work of scholarship on the topic and follow up on the sources used by the author (footnote tracking).
Most of the time you will find the secondary literature you need by using the online catalog, the appropriate article databases, subject encyclopedias or bibliographies, and by consulting with your instructor.
Once you have chosen your research topic, the next step is to decide what type of material you are looking for. Do you want books? Journal articles? The type of material you need determines where you should begin your search.
The UIUC Library Online Catalog contains records for books and journals. Use these when you are looking for books on a topic (subject searching), or when you have a citation to a specific book or journal. The catalog will lead you to secondary sources and to published primary sources.
The online article databases provide citations to articles or, in some cases, links to the actual text of the articles. These online databases are subject-based, and some of them include citations to books as well as articles.
Use the online article databases when you want to find citations to articles on a topic. If the database doesn't provide a link to the full text, once you have compiled a list of articles on your topic, you will need to search the journal titles (e.g., Journal of Modern History) in the Online Catalog in order to determine their call number and location (departmental library, such as History, Philosophy and Newspaper Library, Architecture and Art Library, or the main bookstacks).
Some of the online information resources you will be using offer searching by subject terms, descriptors or headings, while other offer only keyword searching. In terms of formulating your search strategy, this is a key distinction. Records in the UIUC online catalog and most of the article databases have searchable subject headings, whereas many collections of digitized journals and newspapers support only keyword searching. For older digitized material, you have to use the language used by the author when doing keyword searching; there are no subject headings to describe the author's topic. Doing keyword searching in 18th or 19th century books and periodicals requires imagining the language that was in use at the time of writing. Concepts that are conveyed by terms coined by contemporary scholars must be searched using other, era-appropriate terminology.