Land for sale in Sussex County recently totaled nearly $493 million and around 100,000 acres. Based on the combined acreage of land and rural property for sale here, Sussex County has the most land for sale of all counties in the Diamond State. Of all locations in Sussex County with farms and rural land for sale, Lewes had the most land for sale. Sussex County is the largest county in Delaware (1,196 square miles, or some 100 percent of the state's total land area). It's located in the Southern Delaware region of the state.