They are currently behind the Kawanis fairground, right by the Griffin airport, and the driving range/second hole of the Griffin City Park golf course. If you turn at the fairgrounds, there is a dirt road that keeps ongoing--follow it, and the bridge parts are right before the woods--just a month ago my children and I explored them.
The historic trusses are supposed to be in storage at an airport: http://www.griffindailynews.com/view/full_story/17987259/article-Bridge-to-be-moved-Monday-morning?instance=home_news_lead_story
This bridge is currently being removed for a newer one. I am a Griffin resident and hate to see it go.
Have a look at the color postcard reproduced as part of the photos for this Frisco railroad bridge at Fort Smith, Arkansas, from the 1880's. The trusses (the flat topped ones) are similar, if you remove some of the scroll work at the top. The scroll work is not absolutely essential to the stability of the bridge as it is under the cross-bracing.
This bridge is scheduled to be replaced by the GDOT during 2010. Arrangements have been made to save the truss structure for the city of Griffin. We have been unable to gather much information about the bridge. There is a picture of the bridge being assembled , dated 1906. We have no information about the company that manufactured the bridge. There are no markings on the bridge. There is some speculation that it was a railroad bridge originally, then as rail loads got heavier this bridge was replaced from its original use and the city of Griffin became the owner and used it for vehicle traffic.
I am hoping that someone reading this might help me in my search.