Initially it operated with Illinois Central 121, the last of the 1930s fixed-consist articulated streamliners built in the United States.

[2]: 23  The Green Diamond required a single consist to operate, departing Chicago for St. Louis in the morning and returning that same evening.

[2]: 22 Conventional equipment with expanded seating capacity replaced the articulated streamliner in 1947.

Amtrak did not continue the Governor's Special, which ended revenue service on April 30, 1971.

"[1]: 31  Motive power was provided by 1,200 hp (890 kW) EMC Winton 201-A 16-cylinder engine.

In June 1968, service between Springfield and St. Louis was discontinued and the remaining segment of the former Green Diamond was renamed the Governor's Special.