Northern Wisconsin was ravaged by a series of huge forest fires after the virgin pine was logged off. The logging left huge masses of dead fuel in the forests, which could be ignited by lightning or sparks from trains and other human activity. Huge fires swept across Wisconsin in both 1931 and 1933, so the CCC was given the primary mission of cleaning up the forests, replanting trees, controlling erosion, and building fire breaks. Once that mission was making progress, the CCC started building infrastructure for fighting fires, and also improving parks and recreation areas.
The CCC established Camp Riverside along the Saint Croix River in northeast Burnett County. A key project undertaken by the CCC was to improve an old forest road though the area to provide better access for firefighters. This road is the Saint Croix Trail. They had to build a bridge where the trail crossed the Saint Croix River. I have not been able to find photo or description of the original bridge, I can only assume it was well built like other CCC bridges proved to be. It was likely a timber bridge.
The original CCC bridge became obsolete, and was replaced in 1983 by the current concrete bridge. The new bridge is unique in several ways. First, it is the only bridge over the Saint Croix River on a gravel road. Second, it is the least used highway bridge to cross the Saint Croix River. And third, it uses a unusual construction method that has not been seen on any other bridge over the Saint Croix River, which is the continuous slab method. To get started, piles were driven at each end of the bridge and for the center pier. The center pier was built. Abutments were built at the ends, complete with concrete wings to retain the highway embankment. Next comes the unusual part. Normally, a set of girders would be placed across the spans. But in this case, no girders were used. Rather, wooden falsework was erected to hold concrete forms in place to build the deck. Rebar was placed in the forms, and concrete was poured. Once the concrete was cured, the falsework was removed. Once the falsework was removed, the finished concrete deck was self-supporting and holding itself up crossing the two spans. All that was needed to finish the job was to add guard rails.
The photo above is looking southeast down the length of the CCC Bridge. The river flows to the right in this view. Note the open style of guard rails, which is now considered to be obsolete given that snowplow can toss road debris into the river, and rain can was road contaminants into the water.