In fact, I thought it was Futura at first... then noticed that very un-Futura vertex on the ’M’ that only drops to the x-height. This font appears to be the similar to the font on many other public buildings—schools, post offices, etc—built in the 1950s and 1960s around the Twin Cities.

FWIW, this is the Minneapolis Fire Station #7 on E Franklin at Cedar.
I love the curved stroke on the ’7’.