A tonneau system for a cargo box of a vehicle having a support frame connectable to the cargo box. A cover spans the support frame and is positionable between a tensioned position and an untensioned position. A bow member is coupled to the cover and is moveable between a first position and a second position in response to the movement of the cover between the tensioned position and the untensioned position. A retaining member is then operably coupled to the support frame. The retaining member retains the bow member when the bow member is in the first position and releases the bow member when the bow member is in the second position.