The Library of Congress' American Memory collection is a great online source of materials. To demonstrate, I have pulled a few examples from Boston. They illustrate how even some innocuous sites may have a special history.
Here is Harry Houdini preparing for his Harvard Bridge jump...
There are quite a few available aero-maps of Boston.
And the Revolutionary Era maps of the city are revealing.
And HABS/HAER has drawings and photos.
Explore and enjoy.