Often, the best work arises from close engagement with a primary source. As you read, you'll think of questions or begin to shape an argument. The hard part is to find a primary source that addresses the broad general area of interest. Here are some strategies for finding primary sources:
Different library catalogs have different interfaces, and Princeton's library catalog currently offers two, the old Main Catalog and the new Books+. But no matter what catalog you're searching, there are some strategies that can help you find primary sources.
To find the papers of an individual, search for that person as an author, e.g. jackson, andrew
To find the records of an organization or government body, use the name of the organization as an author e.g. United States. Dept. of State
Include one of these words as a keyword or a subject:
If you find something that looks useful, look at the detailed view of the catalog record and try to identify the "subject" assigned. For many topics in history, there's an official term used in all Anglo-American library catalogs, like:
To find works published in a particular time and place, explore the search options. It is usually possible to limit your search by date, language, or location of publication.
The primary sources for understanding Latin American history -- newspapers, government documents, political pamphlets, personal memoirs -- were written in Spanish or Portuguese. You will find key documents and the memoirs of important people in translation, but by no means has all the relevant material been translated. So, If you only read English, you will need to look at your topic through the lens of an English-speaking country, likely the U.S. Some places to start:
For news in translation see the Foreign Broadcast Information Service