Old Iron Bridge over the James River at Pony Pasture Falls near Brown's Island in Richmond, Virginia. I believe that this is a Civil War era bridge that the Confederate Troops used to escape the fall of Richmond to the Union Army.
not too dampen your spirits,but...
it's a light rail bridge. propably to transport coal trucks across the river.
the concrete footings are too modern for the civil war period.
the longest bridges of the period would be stone, wood and stone,
brick and wood or the largest ,like at appamattox, brick pillars and stressed steel trusses.