Found information from the Milwaukee Road Archives. The bridge was indeed relocated from a swing bridge in Milwaukee, however the original date of construction is unknown
Well, I hope you start with the archive! Even at 17 falling from one of these would do damage (to you).
Perhaps some additions to the "related" section would help connect the similar designs.
Clark,
I strongly suspect the Spring Green bridge is a prime example of this type of structure, before modification. However, the easiest way may be to pull blueprints from the CMStP&P archives, as they would have an annotation. But a 17 year old can scale a truss as well! :)
What would help is finding a similar span still in original location/configuration. If these were at one time movable there ought to be signs of the pivot ring and some additional structure on top.
Then we draw straws to see who gets to climb around to look for them. (Those who remember Pearl Harbor Day can be excused!)
Art,
It's exactly what I'm suggesting. The 1911 stamp clearly isn't accurate for the spans, as those look to be 1880s pin connected spans. Those spans are far lighter (Picture 13).
I think the second, and likely most accurate piece of evidence would be the vertical endposts. Other than it being two relocated pieces of a center pivot swing bridge, there would be no point for a design like this.
Center Pivot Swing Bridges were typically frowned upon by the turn of the 20th century, as they were much more complex. Compared to a swing span which is composed of two trusses, and a tower on the swing pier, a center pivot was typically two trusses, joined over the mid point of the swing pier. See this example, also another Milwaukee Road bridge.
http://bridgehunter.com/wi/richland/bh50335/
Interestingly enough, two years later, a similar span would be built at Rock Valley, Iowa. Once again, for 1913, the span is way too light, and was likely pulled off either the line across Iowa or the line across Minnesota the year before, when both were reconstructed for double track capabilities. The bridge looks like it was originally constructed in the late 1890s, being much younger than the example here in Minnesota.
http://bridgehunter.com/ia/sioux/kiwanis/
The question for both of these structures could be answered through the Milwaukee Road Archives, which is a project I will engage in.
John,
Are you suggesting they took pieces of a swing bridge and incorporated them to produce this bridge? Would that explain the vertical endposts of each span at the center pier shown in picture 14?
Regards,
Art S.
Bridge looks like a former swing span, and the trusses are definitely older than 1911.
http://www.austindailyherald.com/2015/10/bonding-with-the-st...
The city of Austin is looking for money to turn a flood prone area into a trail, and convert this bridge to trail use.