Work began in 1851 under an estimated cost of $2 million and ended in 1875, having used $21 million. At its completion, the tunnel was the world's second-longest, after the Mont Cenis Tunnel through the French Alps. It was the longest tunnel in North America until the 1916 completion of the Connaught Tunnel under Rogers Pass in British Columbia. It remains the longest active transportation tunnel east of the Rocky Mountains, and as of 1989[ [update]] is the sixth longest railroad tunnel in North America. The American Society of Civil Engineers made the tunnel an Historic Civil Engineering Landmark in 1975.