I think you are quite right that your tree is a Cherry or Plum (Prunus sp.) of some sort. What species may require additional information. You should always start with a picture of the WHOLE tree, and then gradually collect photos of its various detailed parts.
If this was a decent sized shade tree, I'd venture that it is a Prunus serotina - Black Cherry. Smaller and/or shrubbier trees would lead one to think of the native plum species or one of the more diminutive tree-form cherries.
