I spent an enjoyable early morning reading all the links, and are a bit surprised by how many of the sites I've already been to.
I have personally visited:
Stone Mountain carving (Stone Mountain half)
Independence Hall (Gold $2.50 Sesquicentennial)
Diamond Head (Hawaiian half)
The Alamo (Texas half)
Balboa Park buildings (San Diego half)
Old Swedes Church (Delaware half)
Bay Bridge (Bay Bridge half)
Burnside Bridge (Antietam half)
Concord Minuteman and Lexington Old Belfry (Lexington-Concord half)
I'm half way through the list! Perhaps there is hope that someday I can see all of them.

Thanks to @commems I now have a defined target.
