The Walnut Street Bridge, now referred to as the Old Toll Bridge, consisted of a short bridge on the Wisconsin side of the Saint Croix River, a half-mile long causeway, and then a spindly structure over the main channel. A new bridge was built for US-12, which resulted in the Old Toll Bridge being closed in 1951, and later, the main channel span was removed.
The main channel span had very steep steel ramp, followed by a truss section over the main channel, and another very steep steel ramp going up the hill on the Minnesota side. What was unusual is that the main channel truss was basically flat, while the ramps on either side were very steep. Old timers recall that Ford Model T cars often had a hard time climbing the bridge on the Minnesota side of the main span. Those cars had a transmission with metal bands. As the bands wore down, they would begin to slip. Drivers often found that they could back up the hill since reverse was used much less and the reverse band in the transmission would not be wore down.
What remains today is the causeway, the backchannel bridge on the Wisconsin side, and the piers for the main span. The causeway is a park used by joggers and bicycles. There is a very nice small beach at the end of the causeway. While the causeway is closed to public traffic these days, tour boats do tie up to the causeway, and service vehicles are allowed to bring supplies and repair parts out to the boats.
