Cubs history: Exactly when was this photo of Lou Brock taken?

Last week when Lou Brock passed away, BCB’s Sara Sanchez wrote this article about the Brock trade to the Cardinals, which I commend to you to read if you haven’t.

I mention this article again today not just for that, but for the photo she chose, which you can see at the top of this post. It interested me for historical reasons — when was it taken and who are the other players visible?

Here’s a larger version of the photo:

The ballpark is obviously New York’s Polo Grounds.