Appearance: Fantastic Four #45 (December 1965).
Appearances: A very long list of others.
Years Active: 23,000 B.C.E. to the present.
25,000 years ago the alien Kree visited Earth and performed a series of genetic experiments on Cro-Magnon men. The results of these experiments were a superpowered race who soon split off from the Cro-Magnons and formed their own society. This race called itself the "Inhumans." (Which seems a strange thing for a race to call itself, but oh well.) Since that time they have been active on Earth to varying degrees, sometimes wandering, homeless, but more often living in their hidden city of Attilan.
The Inhumans are very long-lived, with lifespans much greater than that of ordinary humans. Of the current group of Inhumans, like the Royal Family seen above, various stories have shown them in action in the years before the Fantastic Four stole their rocket and went into space. Black Bolt destroyed a Kree ship in the late 1940s, and Triton has been shown as being active at the time of the Titanic sinking.
Useful Inhumans Site
Inhumans From Marvel's site.