Built during the Revolutionary War, construction began in 1778 and was completed by April of 1779.
Between 1779 and the end of the war, Fort Warren operated in tandem with Forts Rutland, Ranger, and Vengeance in defending Vermont inhabitants on the "northern frontier," the military front declared by the Board of War between Vermont inhabitants and the "enemy."
Everyone living above said line had been cautioned to move south, as their safety could not be guaranteed by the state.
[1] The fort never encountered an enemy force like the one that had raided and skirmished with several Castleton residents in 1777, and it was deconstructed or otherwise dismantled when the Vermont Troops were disbanded in 1782.
[1] Kinney, Joseph E. "The Cruel Indifference of Time: The Evolving Public Memory of the Eighteenth-Century Fortifications of Rutland County, Vermont."