Hearts of Steel is a comic miniseries published by IDW, now available in trade paperback. It is set in an alternate continuity in which the Transformers' first contact with humanity is in the late 19th century, not the 20th. Most of the Transformers thus take on the form of fanciful locomotives and railway cars, rather than automobiles, etc. The main exceptions are Shockwave, who becomes an ironclad ship, and Starscream, who becomes a triplane (despite the fact that airplanes did not exist in the 19th century). John Henry and Mark Twain, along with other historical figures, appear in the comic. Optimus Prime and Megatron do not appear, though concept drawings for them are included in the trade paperback.
It is also worth noting that the backstory of this comic assumes the Transformers came to Earth during the age of dinosaurs, and fought a war there and then using dinosaur altmodes, before going into hibernation until the 19th century.