This bridge is a rare example, and the only known example in Minnesota, of a skewed stone arch bridge that follows the helicoidal method for producing the skewed arch bridge. This method was common on bridges in England, but not in the United States. In fact, skewed stone arch bridges of any type are exceedingly rare, and many of those that are skewed use a structurally inferior ribbed design method. Consult the above historical articles and National Register nomination for a detailed discussion on this skew, the form it take, and its reasons for use. In short, the skew helicoidal design of skew allows for the stones to be cut of consistent design and as such allowed United States stone masons who were not used to cutting more complex shapes of stone to construct the needed masonry. At the same time, the design avoids the structural inadequacies of a ribbed approach to producing a bridge skew. Adding to the bridge's complicated design is that its two spans are not the same length, and the bridge also was constructed with a grade. The bridge was designed by William Albert Truesdell. The contractors for the bridge included M. O'Brien of St. Paul who constructed the substructure, specifically that up to the spring line. The rest was built by the McArthur Brothers of Chicago, Illinois. The bridge was originally built as a grade separation to carry 7th Street over the St. Paul and Duluth Railroad. Today, it crosses a rail-trail, the railroad line having been abandoned. The historic integrity of the stone arch bridge is outstanding with no major alterations noted. With the rail-trail underneath, visitors can easily view the spiral pattern of stones in the barrel of the arch, testimony to the helicoidal skew design.
This bridge is tagged with the following special condition(s): Helicoidal Arch
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