I just assumed this was Castanea sativa because, you know, every chestnut I post as something else turns out to be C. sativa. But today I met the homeowner, who planted the tree, he doesn't remember when but some time after he moved there in 1960. He told me it's Chinese Chestnut, which would be Castanea mollissima. That's supposed to have coarsely-toothed leaves with hairs, at least on the young leaves. Or small fuzzy leaves, which isn't all that convincing here. The largest leaves were about the size of my (fairly large) hand. Photos from July 17 and today, August 8. The walnut trees the owner bought at the same time were not the species he was told they were, so I'm just checking whether this tree is really Castanea mollissima. Thanks.
Crown and leaf shape generally correct. If hairiness does not seem right remember that hybrid chestnuts involving multiple species are grown. Unless very few of these are present there you are not going to be able to get every specimen encountered to fit one of the three primary species.
Thanks, Ron and Michael. It's a nice tree, with a lot of (edible) nuts coming along. I see that this species is particularly blight resistant and therefore used in cross-breeding with American Chestnut.