I have a good friend who is the pre-eminent expert in the area on all those old greenhouse properties. if you have specific questions I would be happy to put you in touch with her. She managed many of those properties in the 70’s and 80’s prior to becoming a realtor. She has long standing relationships with all the old timers. No one is even close to as knowledgabe about this issue as her. Her boyfriend is also one of top civil engineers in the county and his firm has done a very high percentage of the planning work for the largest developments throughout SD.