Hi lawnranger,
Here are some ideas for the kind of information that might be help in getting started.
Did Charles CLIFFORD also go to US? (This is not quite clear in your post)
Are Charles CLIFFORD and Mary HART a married couple in a later part of your family tree?
Is it the Irish origins you are wanting to learn more about, or their later life?
You seem certain about Mary HART's birth year, what records have you used for the information?
By starting with all you do know, we can possibly progress to what you do not

Sue