1917-1952 changes were indicated as they occurred in color coding on 200 plan size folded maps on file at Dept.'s Design Section.

Michigan's historic highway bridges are rapidly being torn down and replaced as they deteriorate or become unable to support increased traffic volumes and loads. While the state has the responsibility of providing safe bridges, historian Charles K. Hyde maintains that the state must also preserve many of these remaining historic structures to insure that future generations will have them to view and appreciate. In Historic Highway Bridges of Michigan, Hyde identifies Michigan's historically significant highway bridges within the broader contexts of American bridge design and construction in the 19th and 20th centuries. The book summarizes the improvement of highway bridge design in the United States and compares Michigan's experiences with national trends. To aid the reader interested in visiting the historic highway bridges of Michigan, regional maps show the location of bridges included in the text.