Fire insurance maps, with their incredible detail, are always a great find; we’ve got a couple in local collections here, and I just think they’re magnificent. Unfortunately, they originally had onerous copyright restrictions that prohibited making copies, so these treasures can be kind of hard to find. But the New York Public Library’s Map Division has just put more than 1700 of them, dating from the 1850s to the 1920s, online. Via Maps-L.