Thank you both so much for the information, it is much appreciated!
Dylan,
I just added the Historic American Engineering Record data pages under "Sources", which help explain the long history of this bridge. It appears that the stone piers date from 1822, but the original superstructure was replaced in 1842 and again in 1884. The first iron bridge in the United States was not built until 1839, so any bridge from 1822 would have been either totally wooden (as the original Cartersville Bridge was) or stone. Metal would not have been an option for any of the members in 1822.
That said, this is one neat and unusual bridge! I can't say I've ever seen one like it.
The bridge page states that this bridge was built in 1884, but the news article I found states it was built in 1822. Now that is a seriously large gap, and I feel like there needs to be some clarification here, but I would like to see what sources the creator of the bridge used in determining the age of the bridge, if they still use the site, before I change the date on the page.
While looking around the area at some historic aerial imagery it appears there used to be another bridge across the James between Columbia and Cartersville, so looks like I may have some more research to do.