Any bridge that pre-dates World War II in the Loire Valley is a very lucky survivor. Many bridges were destroyed during the War, by both sides, to disrupt troop movements. You can clearly see the remains of the old bridge between Chaumont-sur-Loire and Onzain in this photo - the grassy hummocks in mid-stream mark the old piers. The new bridge is to the left.
UPDATE: Simon has just found this excellent page (in French) on the history of the old bridge, with a photo of the damage in 1940.