Mark Sickles was elected to the Virginia House of Delegates, 43rd District, in November 2003. He currently serves on the Health, Welfare, and Institutions Committee, the Privileges and Elections Committee, and the Agriculture, Chesapeake, and Natural Resources Committee. A resident of the 43rd district since 1987, Mark moved to Franconia to be close to Fort Belvoir, where he worked at the time for the U.S. Army. He purchased his first home in the Manchester Lakes development and currently lives in Kingstowne. Mark has two Masters Degrees from Georgia Tech and a B.S. from Clemson University. As a part time legislator, he works full time for a national marine construction company and federal government contractor. He attends the Old Presbyterian Meeting House in Alexandria.

Mark began his public service as a volunteer in the local political and civic life of Lee District. He worked on several campaigns, including those of former Delegate Gladys Keating and former State Senator Joe Gartlan. He was a volunteer legislative assistant for Delegate Keating for three legislative sessions, during which she served as the first woman Chair of the Corporations, Insurance and Banking Committee, now the Commerce and Labor Committee.

In 1993, former Supervisor Joe Alexander appointed Mark to serve as the Lee District Trustee on the Fairfax County Public Library Board. In his two years as Chair of the Library Board (1998-2000), Mark oversaw the opening of a new library in Kingstowne, worked to secure funds for a wide-ranging upgrade of electronic resources, won additional funding for books and materials, and oversaw the development of a ten-year capital improvement plan that resulted in the acquisition of over seven acres for the future development of a regional library on Beulah Street near Manchester Boulevard. On the Board for eleven years, he stepped down in December 2003 before being sworn in to his first term in the House of Delegates. In Richmond, he continues to lead the effort to obtain necessary funding for the Fairfax County Public Library that is normally not secured due to a discriminatory funding formula in the budget.

For six years, Mark also served on the Board of United Community Ministries, a non-profit social service agency with a focus helping the working poor in Southern Fairfax County. UCM has an employment training program, an emergency food pantry, operates the Healthy Families program for at risk mothers, provides some transitional housing and operates a first class day care facility called the Bryant Early Learning Center. Mark served as President of UCM in the year 2000.