Two good articles on the early history of this bridge at http://goodspeedhistories.com/ -- search 'Green Sergeant'.
The present structure is a wooden covered bridge resting on a simple steel deck beam span between concrete abutments. After being damaged, the covered bridge was removed in 1960, and two one-lane steel bridges were constructed to replace it. The covered bridge was reassembled onto the north span, and the south span was finished with low stone walls.
The photos below from August 11, 2011, are intended to show some structural details. 1: East end of the bridges. 2: East end, overexposed to show interior of covered bridge. 3: Interior showing wooden structure. 4: Looking south from stream bed, showing the matching steel beams under both bridges. 5: Looking east under the covered bridge, showing the date 1961 cut into the abutment wall, and showing the wood planks that support the floor of the bridge.