The other rail line is the old Soo mainline. That rail line has been abandoned, and is currently used as a regional trail called the Wild Rivers Trail.
At this time, I have not learned anything about the Wisconsin Central Bridge. The railroad path itself is very old, dating from the 1800s. This bridge is not an original 1800s bridge. Rather, the round tubular support piles look like 1980s era work. I suspect that the Wisconsin Central built the current bridge when it took over this line given that the Milwaukee Road was in bankruptcy and was not investing in infrastructure.
Note that there is a small stream entering the St. Croix River from the right in some of the photos below. That stream is the Eau Claire River, and this location is its confluence point with the St. Croix River. The CN railroad tracks cross the Eau Claire River on a similar style bridge about 1,300 feet south of this location.
