I hear that the replacement bridge was constructed in part due to the Meramec Basin Project, which called for construction of up to 30 or more dams throughout the Meramec River Watershed. Construction on one dam was underway when the project was cancelled but there were also plans to construct a dam above Union, MO, which would have backed up water under this very high bridge. The bridge seems a lot taller than is needed for this type of crossing.
Does anyone know about the history of the replacement structure?
Conner has the story of the replacement bridge exactly right. There was a need for a new bridge on Highway 185. The question was whether the dam and lake were going to be built, and whether the bridge needed to be high enough to accommodate them. The Franklin County officials even went to Washington, D.C. to testify before a Congressional committee, urging that decision be made one way or the other. This bridge was cited as a prime example of the need for a decision. The State apparently felt they couldn't wait any longer and in the early 1970s built the new bridge very high in expectation of the lake coming into existence. As it turned out, the lake and dam never materialized and much more money was spent on the bridge than necessary. People just passing through today probably wonder why the bridge was built so high.