What century were the Leiper Canal and Duluth Ship Canal built?
Duluth Ship Canal The Duluth Ship Canal is an artificial channel cut through Minnesota Point, providing direct access to Duluth harbor from Lake Superior. Begun privately in 1871, it was put under federal supervision and maintenance several years later. It is still an important component of the harbor facilities.
Seventh Street Improvement Arches The Seventh Street Improvement Arches are a double-arched masonry highway bridge that formerly spanned the St. Paul and Duluth Railroad tracks in St. Paul, Minnesota. The Seventh Street Improvement Arches are historically significant for its rarity and the technically demanding nature of its skewed, helicoidal spiral, stone-arch design. The bridge is one of the few of its type in the United States, and is the only known bridge of its type in Minnesota. It was built in 1883-1884 by Michael O’Brien and McArthur Brothers of Chicago and was designed by William A. Truesdell. The bridge was listed on the National Register of Historic Places in 1989 and on the American Society of Civil Engineers Historic Civil Engineering Landmarks in 2000.