Locomotive 131 was a Central Pacific Railroad passenger and freight train that ran a one-way circuit on a single track, stopping along its westbound route at the Hill Valley Railroad Station, with San Francisco, California at the end of the line. It was able to complete the circuit in three days, and normally cruised at 25 miles per hour with a top speed of 55, although "fearless" Frank Fargo allegedly pushed the speed to nearly 70 past Verde Junction. The engine was a wood-fired 4-6-0 (two axle leading truck followed by three driving axles) steam locomotive.