The Tehachapi Loop: A Train Crossing Over Itself

Fifteen miles east of this freeway, there is a piece of railroad engineering that has not been improved upon in one hundred fifty years. It is still in daily use. A Union Pacific freight train passed over it this morning.

The problem was simple and impossible: in eighteen seventy-six, the Southern Pacific Railroad needed to build a line from the floor of the San Joaquin Valley up to Tehachapi Pass. The grade was too steep. The locomotives of the era could not climb it without stalling.

You cannot simply reroute a mountain range. William Hood, the Southern Pacific's chief engineer, built a spiral. The track curves in a complete three-hundred-sixty-degree loop, about twelve hundred feet in diameter, with the full loop of track stretching nearly three quarters of a mile.

At the point where the loop closes on itself, there is a tunnel. The track coming out of the tunnel is seventy-seven feet higher than the track going in. The total loop is less than three-quarters of a mile long.

The grade never exceeds about two percent. Gravity does not win. The American Society of Civil Engineers designated the Tehachapi Loop a National Historic Civil Engineering Landmark in nineteen ninety-eight.

The designation is for structures that represent fundamental advances in the field. This loop, completed in eighteen seventy-six, qualified. Here is the detail that makes it worth seeing: a Union Pacific freight train today can be long enough that, while the locomotive is already on top of the tunnel, the rear cars are still passing under it.

The train crosses over itself. You can watch the headlight of the engine moving above the boxcars behind it. To get there, take Highway Fifty-Eight east from the Interstate Five junction near Wheeler Ridge, then continue east about fifteen miles to the town of Keene.

The loop is visible from the road. It is not marked with a large sign. It is just there, doing what it has done since Grant was president.