The Library of Congress has a great tool for helping you evaluate potential primary sources:
The Internet History Sourcebooks Project is a collection of public domain and copy-permitted historical texts presented cleanly (without advertising or excessive layout) for educational use.
Primary source research requires a slightly different approach to searching. Here are a few tips/strategies:
Start by doing some background reading or "pre-research": The more you know about key events, people, laws, and especially common terminology used during the time period you are researching the more successful your research will be. See the "Getting to Know Your Topic" page in this guide for help.
Limit to specific time periods: When searching for primary sources online always remember to use date ranges (usually on the advanced search page) to focus your search.
Use primary source keywords to find primary sources: Use search terms that reflect the types of primary sources you’re looking for, such as: diaries, pamphlets, correspondence, speeches, manuscripts, personal narratives, interviews, firsthand, eyewitness, sources, etc.
For example: slave AND diary | suffrage AND pamphlets | united states and race relations AND sources
Primary sources are items that are directly associated with their producer or user and the period in which they are created. They reflect the authority and perspective of someone who directly experiences what they are detailing.
Primary sources can be found in: