You've piqued my curiosity. Would you tell me when you think literal OT history begins, and the reason for your choice?
I'll share first. I think literal history begins in Genesis chapter 2 (and perhaps even in chapter 1 if the creation of the universe was anything like the cosmologies of Humphreys or Hartnett). And one of the reasons I believe chapter 2 and onward is literal is because in places like Luke's genealogy and the gallery of faith in Hebrews 11 the NT speaks of those earliest people no differently than it speaks of later people.
First, the phrase "literal history" makes no sense. "Literal" applied to a text refers to the level of meaning of a word, phrase, sentence. A "literal" meaning of any text is that where the common sense meaning (usually an empirical meaning) is intended. So where "day" is used literally, it means either the period between sunrise or sunset or the period it takes the earth to make one full rotation on its axis (i.e. a day and a night).
But this meaning doesn't imply that the text in which it occurs is history. It could be a novel, a doctor's prescription (take one tablet each day), a weather report or a poem.
"history" has a different meaning altogether, and typically refers to events which were recorded in such a way that we can verify them from documentation. Though we must also make allowance for oral history as well. While it is not as easy to verify history handed down orally, there is often genuine remembrance of actual events in such histories. In my country, our Supreme Court has recognized the oral history retained in the traditions of indigenous people as admissible evidence when establishing land claims.
Given the very different meanings of "literal" and "history", one referring to semantic meaning and the other to records of events, and given that records of events need not be literal and literal texts need not be historical, it makes little sense to couple them.
I expect what you are really asking is where in scripture can we be sure that the events in the narratives are about actual people and actual events.
Since there is almost no documentation of any biblical figures or events outside of scripture itself, there is very little of it we can verify as actual history. We certainly cannot draw a line at one point of scripture and say "everything before this is not history and everything after it is not." It is much more piecemeal than that with historical narrative and non-historical narrative entwined with each other all the way through.
Of course, there are delightful exceptions, where the existence of a biblical figure or event is confirmed from non-scriptural data. The best known is probably Hezekiah's building of a tunnel to safeguard the water supply of Jerusalem and his resistance to the Assyrians. The first has been verified by archeological work in Jerusalem itself and the second by the court annals of Sennacharib.
For the New Testament we also have records confirming the actual existence of political figures such as Herod, Annas & Caiaphas, and Pontius Pilate. We do not have confirmation of the existence of Jesus of Nazareth, nor of his execution.
So where does that leave us? In most cases we need to evaluate the plausibility of the historical existence of biblical figures and of the stories handed down about them until they were consigned to written form.
Being unable to document that a person actually existed does not, in and of itself imply that they didn't. Without implying that everyone named from Genesis 12 on was an actual individual in history, I would set Abraham as the first plausible historic figure in scripture. I have no doubts about the actual existence of David and his successors. Nor of post-exilic figures such as Nehemiah and Ezra. Daniel, on the other hand, may not be a historical figure. Possibly not Samson either. It's hard to say when the person is presented as a figure of legend. Legends can gather around a historical person, but the stories are still legends. Even many of the stories about people whose historical existence seems more certain are more in the nature of legend than reportage.
Genealogies don't really help much because they didn't function in ancient times as they do now. Often genealogies included eponymous ancestors (i.e. it was inferred from the existence of a people such as the Moabites or Canaanites that they had an ancestor named Moab or Canaan. The inferred ancestor was given his name from the people rather than the people taking their name from the ancestor.) These "ancestors" were listed in genealogies in exactly the same way as known ancestors. We see an example in Genesis 10 where at one point, instead of giving the name of a person, the names of nationalities are listed.
So all in all, story and history, legendary tales about both fictional and historical people and events are interwoven seamlessly throughout scripture from beginning to end. It takes a careful study of texts and how they were used in ancient times, what purpose they were written for, and what the cultural meaning of the stories were to come to some decision as to how they relate to history. And obviously, any decision is likely to be controversial with some scholars granting historical status where others don't.
Sorry, that's a long answer, but the main point is that there is no simple answer. It is not a matter of demarcating that history begins in the bible at one specific place. Not even in the New Testament.