- September 7 – 39-year-old Keith J. Gardner pleads guilty to murdering his 63-year-old mother Jannis, his 64-year-old father Jimmy, and his 90-year-old grandfather Elmer as they slept in their Lorton home on the night of April 30.
- September 13 – After extracting promises that they will upgrade the existing system, including an upgrade to allow customers to use their own cable-ready television sets, the Fairfax County Board of Supervisors votes to allow Cox Communications to purchase the Media General Cable cable TV system.
- Jackman, Tom. "Gardner Pleads Guilty to Killing Parents, Grandfather." The Washington Post: 0. Sep 08 1999. ProQuest. Web. 2 Sep. 2014 .
- Shear, Michael D. "Fairfax Backs Cable Deal After Promise of Upgrade." The Washington Post: 0. Sep 14 1999. ProQuest. Web. 19 Apr. 2014.
|Fairfax County by Year: 1999|
|August 1999||·||September||·||October 1999|