I have available on this website a digitized PDF version of Michigan's Historic Bridge Inventory of 1995. While many of the bridges have been demolished, it is still an invaluable tool in narrowing down where the interesting bridges in Michigan are. In addition the inventory features some interesting stories about Michigan's transportation history. Note that you need Adobe Reader to view these. I recommend right-clicking on the PDF links and choosing Save Target As" and downloading them for offline viewing on your computer. These links are compatible with download managers, so feel free to use one when you download.
The next selection of links are the same content as above, except they are broken into sections. You may find this nice for easier downloading, but these may also be easier to view as you will not be scrolling through so many pages at one time.
This inventory is very old and while it covered a variety of structures, bridges were among the structures inventoried. The majority of highway bridges listed in these documents no longer exists, but may be of interest to get an idea of what once was in Michigan. Unlike the 1995 Historic Bridge Inventory, this survey also looked at railroad-owned bridges. Many of the railroad bridges still stand today. The inventory is thus useful for identifying and learning about Michigan railroad bridges. It provides valuable date and dimension data for the railroad bridges too.