A BCB reader named Steve van Sothen sent me the above photo, saying it was from his first Cubs game and “May 1980” was written on the back.
Those are very good clues; first, have a look at a larger version of the photo:
The scoreboard’s a bit blurry, but there’s absolutely no doubt who’s in the field. It’s the Montreal Expos.
The Expos played a three-game series at Wrigley in May 1980, the 26th, 27th and 28th. May 26 was Memorial Day; attendance that day was 31,845.