Simutronics is an American online games company whose products include GemStone IV and DragonRealms. It was founded in 1987 by David Whatley, with husband and wife Tom & Susan Zelinski. The company is located in Saint Louis, Missouri, with additional offices in Maryland.
The company's flagship product is the text based game, GemStone IV, which has been running for around 15 years. GemStone was originally accessed through General Electric's internet service provider GEnie, later becoming accessible through AOL, Prodigy, and CompuServe before Simutronics finally moved all their games to their own domain in 1997.
Source: Wikipedia, "Simutronics", available under the CC-BY-SA License.