Wikipedia explains that the The Tridge is a three-way wooden footbridge spanning the junction of the Chippewa and Tittabawassee Rivers near downtown Midland that opened in 1981. It consists of one 31′ tall central pillar supporting three 180′ long by 8′ wide spokes. This apparently globally unique structure was built by Gerace Construction of Midland who add:
The walkways are eight feet, three inches wide, and the triangular observation area in the center measures 35 feet per side. The wooden decking and beams filled six train cars. Although the majority of the Tridge is wood, there are 20 tons of steel in the structure in the form of bolts and connectors. A cofferdam – an enclosed circular cell formed from steel sheet piling – was driven into the river bed and then pumped dry to keep water out while the central concrete pier was built. A causeway – essentially a road in the middle of the river – was built from concrete rubble to allow a crane to approach the center construction area.
The Kuriositas has a nice aerial view of the Tridge too!