When to use one; when to eschew one; questions that have plagued writers and English students since the invention of punctuation. I direct you to a website, provided courtesy of steampunk writer Cherie Priest, that answers all your questions and some you didn’t even know you had.
Now I digress. What, you ask, is steampunk? Steampunk is a speculative fiction sub-genre that advances Victorian-era technology in a straight line and is often/usually set in the Victorian era. (Remember that Queen Victoria ruled for a long time.) Imagine steam-powered machine guns, automobiles, etc. In the graphics novel category, an example would be League of Extraordinary Gentlemen. The Difference Engine would be an example of an early steampunk novel. There are schools of thought about whether west-coast steampunk is more “frontier” and east-coast is more urbanized/”Victorian,” and I don’t know about southern and southwestern steampunk. Mostly, it’s fun, and it’s a prose style that allows the writer to indulge in many a semi-colon.