This swing bridge is a less common continuous-style-truss swing span, where it looks like a single span with a pier under the center, rather than two simple-style-truss spans joined at the center to a tower. I was looking at an online (Google Books) historical book the other day that had the correct "technical" terminology to distinguish between these swing span types, but i can't recall which book it was or what terminology. It was a two volume set one devoted to movable bridge superstructures and the other to movable bridge mechanics. An interesting read.
Photo #6 does indeed show a round pier with gearing on top under the center of the north truss, indicating a swing span.
Here's an article that states it, too.
Picture 6 says it's showing the swing span.
This is a truss bridge incorrectly categorized as being a moveable bridge.
The Southside bridge with the swing span was opened in the mid 1970's for inspection, then closed and welded shut. I regret that I didn't take pictures, but I did get to see it.