Historical documents. Most important events were written down by someone who witnessed it happen. Sometimes they're not completely accurate but it's the easiest way to get information.
The best source of historical evidence to learn about how an event unfolded is a newspaper account written when the event occurred. Newspapers constitute one of the most reliable sources of historical evidence due to the fact that it provides facts in terms of actual events. In the newspaper, you can find the date of the event as well as a detailed explanation of how the events occurred. On top of that, newspapers are likely to include facts and figures regarding the event and it is the least subjective source.
