As Ralph mentioned, Waterway Guide has the bridge tables listed with all of the clearances. Be aware that
Florida has re-marked all of their bridges to show the clearance at the bridge for "low Steel". This will be the lowest point under the bridge within the channel. You will have about 4 feet additional at the center of the span and they usually have a sign somewhere stating that. If not, call the bridgetender for the correct clearance. This is for opening bridges of course, so the fixed bridges will be as charted. If you have a sailboat, there are several bridges along the GIWW from
Texas to
Florida that are fixed at 50 feet. If you have a
mast higher than that, it means jumping in and out to avoid these areas. We have done the trip twice with our sailboat and wrote about it on our Sea Trek site. Good luck. Chuck