There is a very large amount of historical information available and more than one way to classify it for easy navigation.
An outline guideline for contributions to Wikipedia in the field of history can be found at Wikipedia History standards.
A caveat about some sources of historical information can be found at Dubious historical resources.
History classified by location: this classification is useful for finding topics that have a geographical focus, such as the history of empires, nations, regions, cities etc.
History according to time periods: what happened during particular time periods at any place.
History of races, nations, cultures, movements, etc., as they developed in time and location.
See also: Archaeology, Historian
How are we working together to find formatting practices we can all support? See Wikipedia History standards