Peter's right. The U.S. tax code was amended a while back to allow farms to be passed on to heirs without being subject to estate taxation. The only stipulation is that the property must continue to function as a farm for a certain period of time. But most of them get sold off anyway because the heirs are not interested in running the family business like their parents did.
My experience is, in the case of family farms, the kids keep the farm and rent it to other farmers to plant and harvest on shares. There was a time, before the value limits were raised, when the farm would be sold to pay taxes.