Tehachapi train loop

One of the engineering feats of its day, the loop was built by Southern Pacific Railroad beginning in 1874.   The first train to use it reached Los Angeles in 1876.  On the loop the track passes over itself, lessening the grade.  The loop gains 77 feet in elevation as the track climbs at a steady 2% grade.  A train more than 4,000 feet long thus passes over itself going around the loop.