Rock Island Bridge is the oldest existing and was only the second bridge to span the Columbia’s 1200 mile course. The last permanent link in the Great Northern Railway’s mainline from Minnesota to Puget Sound opened on June 15, 1893 replacing the steamer ferry Thomas L. Nixon. The steel cantilever truss with a main span of 416 feet was designed, fabricated and constructed by the Edgemoor Bridge Works of Wilmington, Delaware. It was erected by use of novel techniques first employed by railways in Japan. The swift current and deep channel at the site precluded the use of falsework or scaffolding, instead the on shore approach spans were built first and counter-weighted with bundles of steel rail which supported the weight of the main structure until the truss was completed. The bridge was strengthened in 1925 by building a wider and lower truss around the existing structure which was left in place and has carried traffic without interruption for over a century.