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.