The majority of the fleet was assigned to the short-haul (300 miles or less) intercity routes out of Chicago that operate under the Amtrak Midwest branding.

In 1988, Amtrak and Bombardier signed a contract for 104 Horizon cars, based on the Comet railcar, built for use on commuter railroads.

The Horizon cars allowed Amtrak to add capacity to its fleet quickly since it was adapted from a proven design, and Bombardier Transportation was already in full production of Comet II railcars.

Amtrak was also able to finance the Horizon cars privately, making them the first railcars the railroad was able to purchase without securing federal funding.

They are designed with a maximum speed of 125 mph (201 km/h)[8] and ride on General Steel Industries GSI-G70 outboard bearing trucks, also found on the Superliner II (which were also built later by Bombardier).