Your best way to find primary sources is to use the secondary sources. The researchers who wrote those journal articles, books, and chapters have likely done extensive research. Wikipedia entries sometimes include a goodWhen they mention a source that sounds like a primary source (a letter, a memoir, a video, a news story, a photo, for examples), look at that full citation, and try to find it. How?
The DePauw Libraries provides access to the New York Times via a campus site license. Anyone with a current DePauw email account can sign up for a NYT account and get access to the paper and archives on web browser and NYT mobile apps. Find out more about how to set up your account (or renew your access) here.