Located approximately seven miles northeast of Pitkin, Colorado, Alpine Tunnel was the first railway tunnel to cross the Continental Divide and, at 11,523 feet, was once the highest railroad tunnel in the world. Today it is one of the highest closed railway lines in North America. As part of the Denver South Park and Pacific Railroad, the tunnel was completed in 1882 after two years of work. It cuts under the 12,000-foot Altman Pass, located between 12,442-foot Mount Poor and 12,858-foot Mount Helmers. From the east, the old railway proceeded…