Where does history exist? I think it's tempting to say it exists in the mind; however, historical events are not dependent on the mind for their existence. Surely a historical event still exists, even if the mind doesn't exist to comprehend it. How have philosophers handled this problem?
After studying the fundamentals of special relativity and denouncing a neo-Lorentzian approach to time, I am convinced that a tenseless theory of time is best representative model of the given evidence. That being said, under this view, the very events of history are every bit as real and as existent as this discussion. John F. Kennedy's assassination is just as real as the inaugural address given by the 45th president of the United States.
From a slightly physical standpoint, if we were to assume that reality does exist as perceived, all events that you perceive from the outside world (i.e. not originating within your own mind) are necessarily past events as the maximum speed at which information can propagate is the speed of light. This may not seem to be a relevant interjection, but I posit that it is simply because, at the time at which you perceive an event, that precise event is no longer taking place and is, thus, no longer "real" in a tensed theory of time. Ontologically speaking, I would say that past events are in existence in the same way present events are; they exist merely as temporal points on a [perceived] linear timeline, not as a physical object, but as concepts used to describe the temporary nature of things at the given point.