Here’s the key question: Is the Stage Manager an inhabitant of Grover’s Corners?
Ding! Our answer is yes. Our answer is also no. On one hand the Stage Manager constantly says stuff like, "Here in our town, we like…" and he also takes on the characters of various citizens. The implication is that he’s someone who lived (lives?) in Grover’s Corners. He has an attachment to the place. But, he also manipulates time, which is a bit weird. The Stage Manager exists separate and outside of Grover’s Corners, stepping into and out of various scenes at will. He can look at a little boy and tell us that the little boy will die fighting in World War I. He’s omniscient. Ageless. And he can see us. Characters in plays typically aren't supposed to see and communicate with the audience. That means he exists in our time! Moreover, the Stage Manager knows that he’s part of a play. In fact, he wants a copy of this play to go into a time capsule. Whoa. That means he exists even outside of this play! (Could it be that he’s the big man upstairs, a.k.a. God?)
One last thing: Our Town is the Stage Manager’s show – he’s running it. And he’s not agenda-free. Think about the scenes that he chooses to show us, and the point that he’s trying to drive home. He beats us over the head with the idea that life is short so enjoy every moment, even the mundane. The Stage Manager isn’t some objective scientific observer making notes on a clipboard. He’s orchestrating the whole play. And that’s an important distinction.