Land for sale in Canyon County recently totaled $621 million and 5,000 acres. Canyon County ranks fourth out of 44 counties in the Gem State for the total number of acres of land currently advertised for sale. Among cities in Canyon County with land and rural real estate for sale, Caldwell featured the most land for sale. Canyon County is the 38th largest county (603 square miles) in Idaho. It's located in the Southwestern Idaho region of the state.