Does anyone know how to make it? Ideally I'd like to save it as a psd and use it as a layer on a print of a Revolutionary War battle or a map or a conflation of both.
You could use one of these many blood brushes found on deviantart:
Search for tutorials for "Photoshop drip". One is http://photoshop-dragon.com/Tutorials/Text_Effects/Dripping_Blood_Text .htm.