Okay, the classic Steampunk setting is the era of Jules Verne, who lived through most of the 19th century (born 1828 died 1905), and did most of the writing he was famous for started with a meeting with Alexandre Dumas in 1848.
So let's call it the latter half of the Industrial Age, or as some call it "The Age of Brass and Steam".
Mary Shelly, author of Frankenstein, predated him a bit. Her literary career started in about 1820, about ten years before the Industrial Revolution.
Yet her work, while largely a commentary on the nature of man, defines very much the Flesh Golem as we see it in D&D, right down to it beilg "slowed" by fire and healed by Lightning.
So that one is already Steampunk-ish.
Also note the Pathfinder Clockwork Golem, who is already steampunked, and the Alchemical Golem, also Pathfinder.
So there's an easy start for you.