The Firefly was a streamlined passenger train operated by the St. Louis – San Francisco Railway (the "Frisco").

[1] It was intended to compete with the Santa Fe, which had expanded its diesel streamliner service The Chicagoan/Kansas Cityan/Tulsan to serve Tulsa and Oklahoma City.

[3] The Firefly proved popular enough to overwhelm its three-car consists, and mismatched conventional cars were often used to enlarge capacity during World War II.

[6] The Frisco decided to fit its steam locomotives with a cowling, described as a torpedo-type jacket[1] giving it the appearance of a bullet-like projectile traveling down the track.

[8] The driving wheels were enlarged from 69" to 73" by means of extremely thick driver tires, for greater speed.