Short answers, pulled from the story.
Lyon Sprague de Camp was born on the 27th of November 1907 in New York City. He grew up as one of three sons to Lyon de Camp, a businessman dealing in real estate and lumber, and Emma Beatrice Sprague.
During World War II, de Camp served as a researcher at the Philadelphia Naval Yard alongside fellow writers Isaac Asimov and Robert A. Heinlein. He eventually rose to the rank of lieutenant commander in the U.S. Navy as a reserve officer.
De Camp wrote Lest Darkness Fall in 1939, an alternate history novel that helped define the genre and remains in print after more than seventy years. The story rationalized time travel methods while constraining the hero's technical expertise by the technological limitations of the age.
By May 1976, de Camp joined the newly formed Committee for the Scientific Investigation of Claims of the Paranormal alongside astronomers George Abell and Carl Sagan. Despite being a long-time writer of fantasy, he did not believe in ghosts in the supernatural sense and insisted on first-hand unbiased measurable data to back up such assertions.
In April 2011 at a meeting in Denver Colorado, he was selected for inclusion in CSI's Pantheon of Skeptics. The organization previously known as CSICOP created this pantheon to remember the legacy of deceased fellows who contributed to scientific skepticism.