Can you provide a photo of the base of the tree, where the trunk enters the ground?

Can do that tomorrow, thanks. Nothing unusual there that I can tell, though.

Weird. It doesn't look like verticillium, which would be the main cause of sudden death during the growing season. Are you sure there wasn't some root damage from the gas company? Even that doesn't make sense though, synptoms of that would have been evident at leafout, small and/or sparse leaves, rather than suddenly just dying all at once.

We really don't know. My husband said it's like it's been poisoned or something. It's been growing well and absolutely fine up until now. I guess we'll see if it comes back next year, and if not, replace it. I kind of wanted a gingko there, just like them, and I read they make good street trees because they're pretty hardy, but he wanted something native, and I do like the bright orange color of the leaves in the fall. I did notice that a lot of the other trees on the street look like they are planted on a bit of a mound, and ours is not. I am pretty sure he planted it correctly, he's kind of a stickler for that with all the plantings around the house, I'm the one that doesn't follow the rules. BTW, all the leaves are completely dead and brown, now.

I'd guess it won't be coming back next year.
Why not dig it up and look at the rootball.
How about a pic of the base of the tree like mentioned above?
Is the grass there alright?
Gas and water lines would have no affect on the maple unless they were leaking. Is the ground abnormally wet or can you smell gas?
Trees don't die for no reason.
Mike