In this article, we offer an explanation of steampunk and theorize the genre and its functions within Scott Westerfeld's YA series Leviathan. In order to do so, we examine the "cogs" of the genre machine and its use of nostalgic longing for a revised past/future to rebel against present day cultural norms. Critics note that steampunk takes an historical past and either reimagines it or repositions it in the future. This literary form, then, is shaped through a confluence of history, cultural memory, and fictional technologies. In mechanical fashion, the cogs of steampunk move with and against each other to produce and revise an imagined "What if?" We posit that steampunk's complexities might be better understood by examining the parts of the machine, those cogs that make the engine of steampunk work. We identify three major elements--Victorian history, the workings of cultural memory, and the modification of and recombining of past technologies and literary forms into the genre of steampunk--and then apply these to an analysis of Westerfeld's trilogy.