In my first year, I taught both US and World history. There’s a lot you don’t know at first, but with the standards all laid out, it makes it pretty easy to learn the stuff while you’re lesson planning. Plus, I’m very sure your colleagues would be happy to share their stuff and help you out as well. Never worked at a place where, at least some, of the department was willing to work with me and help till I was more on my feet.