First Appearance: Doctor Strange, Sorcerer Supreme #37 (January 1992).
Appearances: Dr. Strange, Sorcerer Supreme #37, Savage Sword of Conan #22.
Years Active: 16^th Century.

"Saint George" is actually Georg von Frankenstein, a German knight who rode off to war against the Turks. In 1531 the "Scheusslischer Lindwurm" dragon emerged from a stream on Magnet Mountain (the "Rock of the Franks," which is what "Frankenstein" means), in what would later become Germany, and began terrorizing the local villages. Hans von Frankenstein, the cowardly head of a nearby town, ordered that a maiden be sacrificed to the beast to placate it. Georg returned from the war and slew the dragon.

His name anglicized, Georg entered the annals of history as "St. George." See the Solomon Kane entry for more on this.

Note: I expressed doubt that the legend of Saint George was of such recent provenance. To this comment, I got the following e-mails:

From Donald Campbell:

You are correct in believing that the legend of Saint George predates 1531 AD.  According to my encyclopdedia, the legend of Saint George saving a maiden from a dragon first appeared in the late 12th century. Legends about Saint George himself were told in the 8th century or earlier.

According to Dr. Strange, Sorcerer Supreme #37, "Saint George" was a member of the von Frankenstein family but it was NOT the same family as that of the creator of the infamous monster.  Apparently, the first von Frankenstein family sold the castle to the state in 1662 AD.  It and the title of "Baron von Frankenstein" were acquired in 1732 AD by one Konrad Dippel and it was one of this Frankenstein's grandsons who created the monster.

BTW, the book In Search of Frankenstein by Radu Florescu pretty much confirms Roy Thomas's story of "Saint George." (Florescu also discusses the possibility of an earlier Frankenstein battling the mortal Dracula, so this book could have been one of Thomas's prime sources.)  There was indeed a Georg von Frankenstein, who died in 1531, and "real-life" legend claims that he did indeed die in the course of slaying a dragon (perhaps "really" a poisonous snake).  Contrary to what your other correspondent reports, this was over a century prior to Castle Frankenstein passing out of the hands of the von Frankenstein family, in 1662.  Thomas never actually said that Sir Georg WAS Saint George, only that he was later REMEMBERED as "Saint George," so later legend-makers (at least in the Marvel Universe, where of course there's no real objection to it having been an actual dragon) may have confused the two.  As I mentioned before, some sources (wish I could remember where I saw this) speculate that the story of Saint George and the Dragon is actually a Christianized version of the story of Perseus and the Kraken; the legend-making process often combines elements of different stories.  Some people in the Marvel Universe might claim that Thor is simply capitalizing on the myths of the Norse god and is seeking on purpose the sort of status that was bestowed on Sir Georg posthumously.

So, give Roy Thomas credit, he didn't really mess up on THIS one.  : )