 In December 2012 , the National Park Service approved the listing of the Upper Twin Falls Bridge that crosses the Menominee River northwest of Iron Mountain . The structure is a single @-@ span , pin @-@ connected , camelback , through @-@ truss bridge , and it is the only known example of its type in Michigan . It was built between 1909 and 1910 because the Twin Falls Power Dam would flood an existing river crossing . The span cost $ 5 @,@ 106 ( equivalent to $ 780 @,@ 000 in 2015 ) , paid equally by Dickinson and Florence counties . Until the 1930s , the Upper Twin Falls Bridge carried US 2 across the Menominee River . In 1934 , a new bridge was built about a mile downstream , and the highway was rerouted over the new span . The bridge closed to automobile traffic in September 1971 , and the nomination process for inclusion on the National Register of Historic Places began in 2012 . 
