Steampunk as a subgenre of fantasy/science fiction was a culmination of the 19th century industrial revolution and the discovery of the ability of the steam engine.
This discovery brought the world together through the advent of easy travel and it truly seemed, to the human race worldwide, that there was nothing impossible through modern technology. Though the mechanics of the steam engine were soon to be overshadowed by the superior availability and ease of access produced by the combustible engine, in it’s various forms, the minuscule correlation of levers and gears that are inherent to the cybernetic function of the steam powered apparatus intrigued every mind that held even a modicum of scientific endeavor. Beyond that, the basic concept was also intriguing on a creative, and (some would even argue), a spiritual level, and the art of steampunk was birthed as well.
Unfortunately, with the advent of industrial technology came the ability to wage war on a greater, more destructive level, and weaponry became inherent in the concept. The gasmask, which became an icon of control and warfare was also integral in the advent of the steampunk genre as art. And no steampunk advocate, to this day, can consider their steampunk collection complete without one.