Thanks for the information on this structure. I was visiting Leavenworth and came across this structure while exploring the canyon. I have always wanted to know more about it but never found the time to properly research it.
Thanks for the update, I have modified the overview.
The way your note is worded implies that this bridge carried railroad traffic. The bridge was part of the Great Northern's electrification of Old Cascade Tunnel and it carried the wate line from behind the dam upstream to the powerhouse that was located on the flat spot immediately downstream of the bridge and between the river and the highhway. When the complex was built the main track of the GN was located where the highway is now. Shortly after the railroad relocated through the Chumstick Canyon the state turned the railroad road bed through Tumwater Canyon into the highway.
A railfan who grew up in Wenatchee and is old enough to have seen the powerhouse.