1. Nonconforming uses

When zoning first began, there were a number of existing uses that would be prohibited by the new regimes. Zoning authorities expected these to die out naturally, but in fact, they often persisted for decades, in part because they often had local monopolies – a nonconforming use might be the only gas station in a residential neighborhood, for example. Many supporters of zoning wanted to do more to get rid of such uses. 

Moreover, because zoning often changes – usually in the direction of becoming more restrictive – existing uses that were fine under the previous zoning regime can become newly unlawful. This is especially true when an unanticipated use begins and the rest of the neighbors want to change the zoning in response. But what about the interests of the property owner with the disfavored use, now known as a nonconforming use?