Sundown towns, also known as sunset towns, gray towns, or sundowner towns, are all-white municipalities or neighborhoods in the United States that practice a form of racial segregation by excluding non-whites via some combination of discriminatory local laws, intimidation or violence. The term came from signs posted that "colored people" had to leave town by sundown. Entire sundown counties and sundown suburbs.
Although it would seem that the abundance of these towns would be in the small towns of the South, Sundown towns exist in every state in the Union to this day. They remain so through custom, intimidation, reputation and folk lore.
The Green Book written and published by postal worker Victor Hugo Green in 1936. Among its pages were listed hotels, restaurants, and gas stations were blacks could get basic services.
NOTE: Big Brother Mike referred to Levittown, NJ. In fact the correct location this sundown town was Levittown, New York