While I describe myself primarily as a speculative fiction writer, I do occasionally write historical fiction (or spec-fic with historic elements) and also have an academic background in historic architecture and in the settlement of the American West. When it comes to writing about the past, it’s key to stop (a lot more often than you’d expect, really) and ask yourself “how did they do x back then?” or “did x exist in that decade?”
We take a great many things for granted to such extent that we’re practically blind to them. Things like plastic, living in apartments, PA systems, and not hiring cobblers. It’s also really important to understand that certain things (like electricity) may have – yes, technically – existed in the period you’re setting your story in. But it may not have been available everywhere. In addition to doing research on specifics, one of the best things you can do is find stories (or, if possible periodicals) written in the period you’re working with. You’ll pick up turns of phrase, long-gone gadgets and fashions, as well as a good idea of what people did not have in that era.
My research today yielded an interesting article on rooming houses, which I’ve added to my research links.
Kelly Horn 
I ran into a similar problem with that steampunk piece I’m working on! I had a piece of equipment I was sure was around then (though not mechanized) but then I looked into it some more and realized, d’oh! It wasn’t around until a couple of decades or so later.
The thing is, we *are* altering history, so it’s not like it couldn’t be fudged a little, but it’s unclear sometimes how much we can fudge before making it unbelievable.