A total of nearly 9,000 acres were listed for sale in Sussex County, Delaware, recently; the value of all Sussex County farmsand rural real estate for sale was nearly $432 million. Based on the combined acreage of land and rural property for sale here, Sussex County has the most land for sale of the three counties in the "Small Wonder. Of all farms and rural real estate for sale in Sussex County, Millsboro 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 Delaware.