Dover, NH

Dover's zoning ordinance has long been a model for aligning zoning rules with housing production needs and traditional neighborhood design. All of its residential districts allow—whether by-right or by Special Exception—homes with up to four housing units per structure. (In lower-density areas, these housing types are only allowed in cluster housing developments.) Lot size and setback requirements provide reasonable opportunities to produce housing, with minimum lot sizes for missing middle housing types tending to be less than an acre. Dover Zoning Code, ​​https://www.dover.nh.gov/Assets/government/city-operations/2document/planning/Regulations/Zoning%202018.pdf
An excerpt from the Dover zoning code.