Originally, and to a large extent still, history was written by the victor and openly told a story flattering to the powerful and those who had won. A successful warrior became a godlike hero.

As rationalism took over in the eighteenth century and onward, truth and accuracy began to be valued over propaganda, especially in the university. In reputable circles today, the lessons of the past are valued only if they are based on truth. If history has something important to teach us, the reasoning goes, it must be accurate history or it is merely teaching us a fiction. False history is an attempt at mind control.

No history can be entirely objective, for we bring to our readings of the past the preoccupations and distortions of our historical moment and our own culture. This is why histories are constantly being rewritten. Nevertheless, it is important to try to get the facts straight so that we can derive the correct lessons from the past. This involves relying heavily on reputable primary sources and constantly reexamining our own biases. It takes humility to write good history. Only history that tells the truth (as best as it can) can guide us accurately to avoiding pitfalls in the future.

It is important to be as objective as possible when doing historical research so that your work does not end up having excessive biases.

Of course, it is always difficult to be objective.  We all come to historical research with preconceptions and attitudes that are built into us by our education and by the times in which we live.  However, we must still try to be objective.  If we are not, our conclusions might be inaccurate.  For example, let us say we are going to study the Great Depression.  If we believe going in to our research that we will find that the New Deal was important in ending the Depression, that is likely to be what we will find.  Having such preconceptions can make us prone to bias.

Therefore, we must be as objective as possible so our conclusions will be as valid as possible.

What is objectivity in history?

History, as a discipline of study, is the examination of historical documents (not only the official documents such as manifestos, constitutions, and public records -- licenses, arrest records, awards, and the like, but also public news reports, contemporary commentaries, private correspondences, and the like), to form a comprehensive and accurate description ("picture") of the period of time and place of action being examined and summarized.  This should be done as "objectively" as is possible -- that is, from a balanced and fair viewpoint, without any personal bias, omission of facts not supportive of one's point of view, not reflective of the historian's personal"feelings" about the event.  For example, when discussing the American Civil War, the historian should be objective about his/her view of slavery, or his/her view of war itself.  Objective historical commenting, then is expected by the reader and demanded by the discipline's ethics.  Exceptions are made for personal views in autobiographies, and other times, when the history writer's viewpoint is the whole point of the writing.