The bridges of Anoka County: Romance of the road only
By Chuck Zielin, Oct 1, 2020
Editor’s note: This column is part one of two.
Understanding that bridges provide a key link in our highway system is critical to a full historical perspective of our transportation system. By definition, a bridge is a link between two separate sections of road. Our earliest examples of this are logs placed diagonally across a break in the road/trail, like would have occurred along the Red River Ox Trail, which ran through Anoka County between St. Paul and Pembina in the mid-1800s. Our first engineered bridges were built in the early 1850s along the military road being constructed from Fort Snelling to Fort Gaines (Later Fort Ripley).
These bridges were single sectioned, wood beamed structures built over Rice Creek and Coon Creek, as well as the Rum River. Construction enabled the opening of the northern and northwestern sectors of the state to commerce, industry and immigration. The significance of the bridges cannot be overstated. Minnesota’s population grew from approximately 5,000 in 1849 to 150,000 in 1860 with commerce doubling from 300 carts in 1854 to 600 in 1858 after the bridges were built. Because the Rum River bridge experienced so many washouts, workers replaced it with another wooden structure in the 1860s. This design centered around a series of vertical upward triangles or a “lattice design.” It utilized oak beams, planking, and an arch support running the full length on either side that added a new design element. It was equal to a New England covered bridge without a roof or siding to protect the beams and proved to be short lived. Exposure to the elements, increased usage, and weight bearing problems resulted in the promotion of a structure using the newly created railroad designs and iron to support heavier loads. One of the earliest iron bridges in the state, the design featured two beamed and arched sections with a rock and stone pier in the center and a plank floor.
The appearance of railroads after the Civil War ushered us into new engineering initiatives to accommodate the increase in weight and size. This meant stronger, more durable materials needed to replace wooden beams. However, since the counties and local road supervisors had control over roads and bridges, adoption of new technologies and designs lagged behind the rapidly changing features of our society. Most bridges built were small, wood beamed structures to serve their agricultural economy. The exceptions being those located in high-traffic areas like the Rum River bridge in Anoka and the nearby ferry crossing on the Mississippi River. Demand for a faster, less expensive (free) crossing that could accommodate a greater amount of heavier commerce plus increased civilian movement resulted in the first bridge being built in 1884.
This new structure employed the latest technologies in metallurgy and design. It consisted of four steel spans, overhead arches, and a plank deck. One section rotated so river traffic could pass. The decking unfortunately proved a major flaw. In the final analysis, the decking limited the speed and weight, rendering the bridge out of date by the First World War.
With the huge growth of the industrial economy after the Civil War, people spreading out away from major cities, increasing immigration, as well as the introduction of automobiles and bicycles, the state responded to public pressure by passing a constitutional amendment (1898) that shifted road and bridge concerns to the state. This change helped bring bridge building into a new era of research, conducted in part by the railroads to create new designs. Engineers introduced new metallurgy developments that allowed for stronger and more durable construction materials, including concrete. These factors all came together at the beginning of the 20th century to create, as our state highway department calls it, the “Golden Age of Bridge Building.”
Chuck Zielin volunteers for the Anoka County Historical Society.