User blog comment:Unrulyruby100/The Kaldwin Royal Family and Supporting Documentation/@comment-3410662-20130101071427/@comment-27202257-20130219174702

Oh my God I'm a dumb. The book is Empress Jessamine Kaldwin, a book that I added to the wiki myself back in October. D'oh!

Anyway, I actually found it on the path leading from the music room to the safehouse stairs in Dunwall Tower. It's also in Daud's quarters as well, just as you said, next to a copy of The Royal Protector.

To sum it up, it seems that Jessamine's father was the first Kaldwin to take the throne. That means he is in fact the Euhorn Kaldwin that commissioned Kaldwin's Bridge, and the Kaldwin dynasty is relatively new. That probably means that while their rule has been short, the Kaldwin family must be fairly old. Either that, or that map isn't as ancient as the Overseer makes it sound.