The roots of the MDDF date back to colonial days in the 17th century,[4] but it was formally established in 1917 with the mission "to protect public buildings, water supplies, and other properties".

In 1994, the Maryland Defense Force's missions were expanded to search and rescue, armory staffing, and disaster relief.

[15] The troop acts in a ceremonial and public relations role as a recruiting aid for both the MDDF and the Maryland National Guard.

In order to complete this mission, the MDDF Cyber Security Unit regularly trains with the Maryland Army & Air National Guard.

The 256th CDU consists of five sections: Headquarters, Hunt Operations, Incident Response and Recovery (IRR), Vulnerability Assessment and Penetration Testing (VAPT) & IT Operations The 121st Engineer Regiment acts as a rapid relief engineering unit intended to deploy after an emergency to aid the Maryland Military Department in civil relief efforts.

[22] The Finance Corps of the MDDF is composed of licensed financial consultants, advisers, and civilian energy managers.

[26] Unlike other MDDF guardsmen, members of the 10th Medical Regiment are allowed to serve in backup status and attend only an annual muster one day per year.

[27] In August 2005, on a purely voluntary basis as state guardsmen cannot be ordered to deploy outside the state of Maryland, members of the 10th Medical Regiment provided medical service to approximately 6,300 Hurricane Katrina victims over an eighteen-day period as a part of Operation Lifeline.

[30] As members of the MDDF, these volunteers received military transport, worker's compensation eligibility, and liability protection under Maryland law.

[6] Over 100 of those sworn in with the purpose of taking part in Operation Lifeline elected to remain members of the MDDF following deployment.