(covers information from several alternate timelines)
Mark Stimson was a Starfleet officer in the 24th century.
In 2328, the SS Manoa ferried him from Dytallix B to Epsilon Wiltz IV. He had purchased a return trip; however, for the trip, he had to exercise option B. The record of his voyage was accessed by Lieutenant Commander Data aboard the USS Enterprise-D in 2370 when Data was reviewing data in the commercial transport database. (TNG: "Inheritance", okudagram)
In 2374, he was named as a member of the Research and Development team listed on a dedication plaque for the USS Prometheus. (VOY: "Message in a Bottle", dedication plaque)
In an unknown, alternate future timeframe, he was named as a member of the Advanced Technologies team listed on the dedication plaque of the USS Pasteur. (TNG: "All Good Things..." dedication plaque)