Charles Braxton points out in a TBZ comment that there is a nice summary on the Three-I League in Baseball Reference’s Bullpen section.
You usually don’t find a lot of documentation on the now defunct Midwest-based league anymore so I’m happy to see this. Indeed, you’ll find standings and league leaders for each year of its sixty-year history at the BR Bullpen.
If you browse the page, baseball historians will most likely find names they recognize. Hank Majeski, Joe Vosmik, Tony Kubek, Mudcat Grant,.. and some pitcher named Warren Spahn.
And only in the early-to-mid 1900s Midwest would have team names like the Peoria Tractors, Moline Ploughboys and Bloomington Bloomers.
thanks for passing this on, Charles! A real gem!