Sources are created with specific purposes in mind. For example, reference material has been created to provide basic facts and overviews of topics. Think about what your research need is and then search for the type of resource that would have been created to fill that need.
Primary sources, which originate at the time of an event, are published first. Secondary sources analyze primary sources and are published later. Tertiary sources bring together various sources. Research draws upon primary and secondary sources. The infographic provides some examples and details of each source type.
Information Timeline Graphic by adstarkel. Used under CC BY-NC-SA 2.0
When an event first happens, there is not a lot of information about it because information takes time to create. As your event recedes into the past, there has been time for more accurate and in-depth information to have been created. If you are not finding information on your event, consider where your event is in this timeline. Has there been enough time for a scholarly article to have been written about your event?