- The Soo Line High Bridge, also known as the Arcola High Bridge, is a steel deck arch bridge over the St. Croix River between Stillwater, Minnesota and Somerset, Wisconsin, United States. It was designed by structural engineer C.A.P. Turner and built by the American Bridge Company from 1910 to 1911. The bridge was listed on the National Register of Historic Places in 1977 for its national significance in the themes of engineering and transportation. It was nominated for its exceptional dimensions, beauty, innovative engineering techniques, and importance to transportation between Minnesota and Wisconsin.