In 1940 the Cardinals wore two different caps, an interlocking STL and a block STL. We do not know the reason the Cardinals had two different caps. We do not know the designations for both caps.
The interlocking STL emblem seems more familiar to us for two reasons. One, the modern cap has an interlocking STL, and the team has consistently had an interlocking STL on the cap since 1942. Two, we have seen other STL and SL examples in years prior to 1940, all of which are some sort of interlocking emblem. We have never seen the Cardinals wear a block letter STL like this one. The main similarity this block STL has is to 19th century Browns teams which wore St. Louis on the jersey with the exclamation (!) T.
History Mysteries:
Why did the Cardinals have two different caps in 1940?
What was the designation for both caps? Home? Road?
Is the Block STL a pseudo throwback?
Cardinals Uniforms & Logos 