A lovely little map

What is it about writers and maps? I don't know a single writer who doesn't love them...
...I based a book around one.
This is a map delivered by a spy to the American forces before the Battle of Princeton in January 1777. No one knew exactly who that spy was... which is way too intriguing for me not to write a book about.
I'm halfway through revising my "Revolutionary Romance" The Bee Hive, but finding this picture again is pushing me through the hard parts.