Bismillah...
When did Islamic history begin? Most people would probably say that Islamic history started with the birth of the Prophet Muhammad (saws), or with the beginning of the Quran's revelation, but Prophet Muhammad (saws) wasn't the founder of Islam, despite what your ninth grade global history textbook may have led you to believe. Muhammad (saws) was the FINAL messenger of God, the last in a long line of prophets teaching, living, and experiencing Islam. So you might be better off saying that Islamic history begins with the first prophet, Adam (as). After all, he was the first Muslim, right? Well, he was the first Muslim PERSON, but not the first Muslim. The angels existed before Adam (as), and there were even jinns worshipping Allah. We too often forget that humans are not the only Muslims. The plants, the animals, the mountains, the sky, all of creation is Muslim, all of creation worships and submits to Allah. So I guess you could say that Islamic history began at the moment of creation, because as long as there has been creation, there has been Islam. So learn about the Prophet (saws) and his companions, but also spend time learning what you can about the prophets that came before, Moses, Jesus, Abraham, David, Solomon (as). And don't just study the prophets. Learn about everything, from the beginning, from the formation of the planets and the stars, to the rise and fall of civilizations, to what's happening here and now, because all of history is Islamic history. Wassalaamu 'alaikum wa rahmatullah.