History books and papers are all about interpretation of primary sources. You pick a historical event or trend, and then examine the evidence of the time—newspapers, manuscripts, photographs, letters and diaries, official records, and artifacts. Your writing is an argument on how to interpret this evidence, and part of an ongoing conversation with other historians about whether your interpretation (and theirs) are correct.
To write a history paper, you'll need to consult books, primary sources, and scholarly articles to show that you've examined the evidence, read other historians' interpretations, and that you have something new to add. You may choose to argue for a different interpretation, or present compelling new evidence that strengthens an existing argument.
Primary sources can be accessed in one of two ways: library databases and archives. Large publishing companies collect digitized primary sources and sell them as databases to libraries—the CSU-Pueblo Library subscribes to more than 20 of these. Archives are privately held collections, often at universities and museums. Many archives have digitized their collections and made them freely available online.