Your handy-dandy guide to Municipal Stadiums.
Muni '57 is Kansas City.
Muni '78 is Cleveland, although it is referred to as "Cleveland Stadium" on bbref. But there are 26 ballparks available from 1978, and 25 of them can easily be paired up with other franchises. Since there were only 26 franchises in 1978, Cleveland gets the unmatched ballpark.