I live in a historic neighborhood in the heart of Washington, D.C. It’s not historic in the sense that anything especially important happened here — certainly not in the modest rowhouses that make up the bulk of the neighborhood. What “historic” means, here and in cities across the country, is that this is a neighborhood where buildings are not supposed to change.
The law says window frames on Capitol Hill must be wooden, or something that looks very much like wood. If a front door has two parts and opens down the middle, it cannot be replaced by a single door that swings open from the side. If the house was built two stories tall, it must remain two stories tall — unless the addition can’t be seen from the street.