West Elevation, Looking Southeast
The vertical truss appears to be a component of this bridge, but is an optical illusion. It is not a component of this bridge but is a railroad bridge downriver.
Photo taken by Carla Anderson, June 1990, for HAER
View photos at Library of Congress
BH Photo #120613
It should be noted that Military Street has history with multiple highways.
At the inception of Michigan's trunkline system, this route originally served as Trunk Line 31. (There is no corresponding "M-31" today, probably due to the existence of US 31.) https://img.lib.msu.edu/exhibits/map/MIRoadMaps/1919-lp.jpg
In 1926, M-29 is relocated to Port Huron and replaces M-31.
In 1933, M-29 is replaced in Port Huron with US 25. http://www.michiganhighways.org/listings/M-029.html
In 1963-64, US 25 is relocated to run concurrently with I-94, and this route becomes Business US 25. http://www.michiganhighways.org/listings/HistoricUS-025pg2.h...
Between September 26, 1973, and February 28, 1974, US 25 is de-commissioned in Michigan, with the Business Route becoming an extension of M-25.
Finally, in 1987, M-25 is scaled back to end where it does today, with Business Loops I-69 + I-94 taking its place here. http://www.michiganhighways.org/listings/M-025.html
So...yeah. This only served the Business Loops of 69 & 94 for its last four/five years before its replacement, and those were the SIXTH (!) different highway designation for this road.