On this page are sources of ready-information for questions like, when did Congress pass the Comstock Act?, or, where are Margaret Sanger's personal papers located?
Use also to confirm information you find in places like Wikipedia: these sources tend to be perceived as more credible, so you can cite them in a paper with confidence.
Finally, reference sources often include bibliographies, making them profitable places to begin a research project.
Encyclopedias attempt to summarize the state of knowledge in a field of inquiry. A good encyclopedia can be a valuable starting point for your research.
Two online reference collections that students often find useful are: Oxford Reference Online, and Gale Virtual Reference Library.