Nathan,
I saw that this bridge is now closed...when did that happen? (I tried Googling and came up empty.)
In any case, with this now closed, I double-checked...it appears that this would've been the last through truss still open to vehicle traffic that also sits in a completely rural area in all of Michigan, all the rest would seem to be in either small towns (Portland), cities (Midland, Grand Rapids), or else otherwise aren't that far out of a town (the two in Washtenaw).
Mike: This bridge I believe was closed sometime this year, I am not sure of the exact date. I did confirm with the Branch County Road Commission that it is closed "indefinitely" so we can assume that it is not going to be fixed "in-house" by the county, so its probably either going to be left closed, or perhaps the county will apply for Local Bridge Program funding from MDOT.