Primary sources can include photographs, newspaper articles, transcripts of interviews, and diaries--anything that records what people saw or thought about an event at the time it happened.
DPLA aggregates records from libraries and archives across the country. The Library of Congress's site is only things that the Library of Congress owns. Both have treasure troves of primary sources that might be relevant to your topic. If you find a few good things via a DPLA search, follow the link to the host institution and see if there's anything related that didn't turn up initially.
Lots of public libraries and universities have local collections of archives. Cities usually have record centers. Many have digitized parts of their collections--to find, try searching the web for the area you're focusing on plus "archive" and see what comes up! Look for something called "digital library" or "digital collections."
News publications can be a great way to research events (past and present.) You can see the conversation or debates around an issue as well as how the events unfolded. For more complete lists see our News, Newspapers and Current Events and/or Historical Newspapers research guides.
Search for up-to-date articles from a variety of U.S. and world newspapers. Historical coverage varies a lot depending on newspaper. For further-back newspapers, try Online Newspapers from the Historical Newspapers guide. We have specific subscriptions to the historical backfiles of the New York Times, Boston Globe, Chicago Tribune, and more.
Thousands of newspapers, available in full-page facsimile, with searchable full text. Most are U.S. titles, with some international coverage, and most are fairly small-circulation newspapers. 1700-present.
Access newspapers, wire service report, and transcripts of television and radio programs. Coverage varies by newspaper title but in general only goes back as far as the 1980s.
Similar to Lexis/Nexis. But covers some key newspapers that aren't in LexisNexis like the Boston Herald and Boston Globe. Again, coverage varies by title but generally doesn't go back before the 1980s.