These are the leaves I picked up during today's after lunch walk. Their outlines may be superficially similar, but each is a different species. Nevertheless, the 1st 2 are closely related; both are maple leaves. The 1st one may be sugar maple (Acer saccharum), while the 2nd one is silver maple (Acer saccharinum). The last leaf is sweetgum (Liquidambar styraciflua). Its fruit, visible below the leaf, is covered with soft spines with openings between them.
There are about 6 Acer species in this area. Here are 4 maple leaves.
The 1st and 3rd are, once again, probably sugar maple and the 2nd one is silver maple. But I am not sure about the identity of the 4th one. Is it black maple (Acer nigrum)?