When I moved from a northern state to a Deep South state, I asked a neighbor about another city that was within reasonable driving distance. He told me it was a "sundown town". There weren't any official signs, but local African-Americans knew they weren't welcome there after dark. I'd never heard of such a thing, but he went on to tell me the names of other towns with similar attitudes.
That was in the 1980s, and since then I've noticed that most of the towns on that list were no longer considered "sundown towns". The practice was bad for business, and most of the people who enforced that unwritten law had passed away. There are still a few sundown towns in this area, but there have not been any major incidents involving people of color.