The total value of farmsand rural real estate for sale in Coos County, New Hampshire, recently on Land.com was nearly $82 million. This represents nearly 4,000 acres of farms and rural real estate for sale in Coos County. Coos County ranks sixth in the Granite State based on the combined acreage of land for sale of the 10 counties in the Granite State. Of all farms and rural real estate for sale in Coos County, Lancaster had the most land for sale. Coos County is the largest county in New Hampshire (1,830 square miles). It's located in the North New Hampshire region of the state.